From Res Ipsa Loquitur to Diethylstilbestrol

Among the most troublesome cases for courts in California and elsewhere are those in which the plaintiff has suffered a major injury, wrongfully caused, but the plaintiff cannot identify the tortfeasor responsible. If the plaintiff can identify an injurer over the course of litigation all is well. If the plaintiff cannot significantly narrow the list of potential wrongdoers the tort system is unable to provide a remedy. Difficulty arises, however, when the plaintiff can identify a group of possible tortfeasors, but cannot identify any particular defendant as the one which actually caused his or her injury.

From Res Ipsa Loquitur to Diethylstilbestrol: The Unidentifiable Tortfeasor in California, Maurer School of Law: Indiana University, Indiana Law Journal: Volume 65 | Issue 3 Article 3, Summer 1990.

As a general principle of tort law, a plaintiff must establish a connection between his or her injury and an act or omission of the defendant. Inherent in this requirement is an identification of the defendant as the tortfeasor. The doctrine of res ipsa loquitur, in its ordinary sense, relieves a plaintiff of the burden of proving the precise cause of injury but not of the necessity of identifying the responsible tortfeasor. Thus, to permit recovery by plaintiffs victimized by unidentifiable tortfeasors, doctrinal expansion has been necessary. California courts have responded to the call.

In Part I of this article, I will discuss res ipsa loquitur as a rule of circumstantial evidence and will proceed to trace its doctrinal progression through a policy-driven version of the doctrine to the concerted action and alternative liability theories of liability. In Part II, I will focus on the setting in which the problem of unidentifiable tortfeasors has been most dramatically presented-women injured by the drug diethylstilbestrol (DES). Finally, in Part III, I will suggest considerations for courts fashioning new theories of liability for unidentifiable tortfeasor cases or applying existing tort theories to new factual situations.


A. Res Ipsa Loquitur and Inferences from Circumstantial Evidence

The doctrine of res ipsa loquitur, as it appears in its usual and most familiar form, is a rule of circumstantial evidence. More precisely, it allows (or compels) an inference of negligence from circumstantial evidence where the defendant is unable to present sufficient contrary evidence. The doctrine applies “where the accident is of such a nature that it can be said … that it probably was the result of negligence by someone and that the defendant is probably the person who is responsible.” It is worth noting that the “inference of negligence” permitted by the doctrine is not an inference that a particular act of the defendant was negligent, but is an inference that the defendant did some negligent act which proximately caused the harm in question although the specific cause of the plaintiff’s injury is unknown.

It may appear that the doctrine of res ipsa loquitur, as so stated, is no more than an embodiment of common sense. Surely judges and juries are capable of drawing conclusions from circumstantial evidence without the aid of a doctrine with a latin name. However, the doctrine, by focusing on the likelihood of the essential components of the plaintiff’s case, provides a logical framework for approaching circumstantial evidence. As such, it is a powerful antidote to an unfortunate judicial hesitancy to accept circumstantial evidence. This hesitancy, and the utility of res ipsa loquitur in combatting it, can be seen most clearly in a brief examination of the line of cases following Sargent v. Massachusetts Accident Co. and the commentary those cases have inspired.

Upham Sargent was a young adventurer who disappeared kayaking down the Nottaway River in Quebec. The Sargent case involved the effort of Sargent’s father (the beneficiary of Upham’s accident insurance policy), to collect a claim requiring that he prove by a preponderance of the evidence that the insured died from an accidental injury.”‘ Although the Massachusetts Supreme Court found this burden satisfied, it first made the following observations with respect to the preponderance of the evidence standard:

It has been held not enough that mathematically the chances somewhat favor a proposition to be proved; for example, the fact that colored automobiles made in the current year outnumber black ones would not warrant a finding that an undescribed automobile of the current year is colored and not black, nor would the fact that only a minority of men die of cancer warrant a finding that a particular man did not die of cancer…. The weight or ponderance of evidence is its power to convince the tribunal which has the determination of the fact, of the actual truth of the proposition to be proved. After the evidence has been weighed, that proposition is proved by a ponderance of the evidence if it is made to appear more likely or probable in the sense that actual belief in its truth, derived from the evidence, exists in the mind or minds of the tribunal notwithstanding any doubts that may still linger there.

This language was quoted approvingly in two subsequent Massachusetts Supreme Court decisions finding defendants not to have been sufficiently identified as the cause of the plaintiff’s injury. In Smith v. Rapid Transit, Inc., the plaintiff was forced off the street by a bus, but she offered no evidence other than that the defendant had the sole franchise for operating a bus line on that street. In Tartas’ Case, the plaintiff sued the Workmen’s compensation insurer of one employer, but the court found that the plaintiff’s decedent could have contracted his fatal illness while working for any of several employers.

The meaning of the Sargent court’s “actual belief” dictum has stirred considerable interest in academic circles. There are several possible explanations. A first possibility is that the “actual belief” required by Sargent exists only if the plaintiff shows that the likelihood of the proposition to be proved exceeds fifty percent by some significant margin. This would, of course, run counter to generally understood standards of proof in civil litigation. In addition, contrary to what the Sargent court may have thought, such a rule would in individual cases increase the likelihood of an erroneous decision. Moreover, none of the Sargent cases have discussed the proof requirement in numerical terms.

A more subtle interpretation is that Sargent requires a plaintiff to offer some individualized proof; general statistical evidence, except perhaps in rare instances, is not enough to satisfy the plaintiff’s burden? This position is defended either by asserting that particularistic evidence is necessary to provide a causal explanation, or by arguing that in most cases, taking into account the probative value of the nonproduction of particularistic evidence, the likelihood of the required showing is less than 50% even though the statistical evidence taken alone may suggest that the likelihood is greater. The counterargument is that, in terms of its value in deciding cases, particularistic evidence is not qualitatively different, much less better, than statistical evidence. Moreover, even taking into account the lack of particularistic evidence, the plaintiff’s statistical evidence may be strong enough to make the probability of the truth of his assertion greater than 50%. Although it is certainly relevant if a party that should be able to produce evidence does not produce it, the pursuit of certain kinds of evidence (i.e., nonstatistical evidence, or even noncircumstantial evidence) may interfere with proper factfinding.

A third explanation of the Sargent cases looks beyond the language of the courts to the factual records underlying the cases before them. Read narrowly, the Sargent cases stand for the simple proposition that a plaintiff may not recover if he or she offers no evidence on a crucial part of his or her case. Although cases are best decided by examining the whole of the evidence presented (taking into account, where appropriate, the nonproduction of other evidence), reconsidering the Sargent and Smith facts and concluding that the decisions were supportable does not solve the Sargent problem. The Sargent language, with its ambiguous implications, still creates confusion.

Res ipsa loquitur as a circumstantial evidence rule cuts through the uncertainties presented by the various analyses of Sargent. Application of the doctrine returns the factfinder’s focus where it belongs: to what the facts of the accident say about the likelihood of negligence and the defendant’s connection to it. If the facts of the accident are such that its cause was more likely than not the defendant’s negligence, the burden of proof shifts to the defendant. The degree of conviction in the factfinder’s mind and the type and quantity of evidence before the court are simply not in issue. Although this approach is proper for all negligence cases, it is most valuable where the complete story of the plaintiff’s injury is unavailable and the factfinder may be tempted to throw up its hands in confusion and to not weigh the evidence before it.

Notwithstanding the relatively simple concepts behind the res ipsa loquitur circumstantial evidence rule, California courts have experienced a great deal of difficulty in applying the rule. This difficulty has resulted from the problems inherent in reducing a rule to a formula and mechanically applying that formula without regard to its underlying purposes.  The starting point for the modern statement of the doctrine is the Wigmore formulation:

  1. the apparatus must be such that in the ordinary instance no injurious operation is to be expected unless from a careless construction, inspection, or user;
  2. both inspection and user must have been at the time of the injury in the control of the party charged;
  3. the injurious occurrence or condition must have happened irrespective of any voluntary action at the time by the party injured.

It may be added that the particular force and justice of the rule, regarded as a presumption throwing upon the party charged the duty of producing evidence, consists in the circumstance that the chief evidence of the true cause, whether culpable or innocent, is practically accessible to him but inaccessible to the injured person.

The California Supreme Court quoted Prosser’s restatement of Wigmore’s formula in Ybarra v. Spangard, and this language has been cited frequently.

In unidentifiable tortfeasor cases, the requirement of most concern is the second one-the requirement that the injury-causing instrument must have been under the “control” of the defendant. California courts have sometimes viewed this requirement as being simply a way of determining whether an injury was the result of the defendant’s negligence. More often, the control requirement has been treated as a special element to be shown. As a consequence, courts have in some cases applied res ipsa loquitur without sufficiently examining the possibility of negligence on the part of someone other than the defendant and, in other cases, courts have had to stretch the control “rule” so as to enable the plaintiff to proceed. Prosser’s remark that:

it would be far better, and much confusion would be avoided, if the idea of “control” were to be discarded altogether, and if we were to say merely that the apparent cause of the accident must be such that the defendant would be responsible for any negligence connected with it.

The problem presented by the unidentifiable tortfeasor cases, however, is fundamental and does not turn on whether the requirement is cast in terms of the defendant’s “control” of the injury-causing instrument or its connection with the alleged negligence. Where the facts disclose multiple defendants acting independently, no one of which more likely than not controlled the instrumentality or was connected with the negligence, no case-circumstantial or otherwise-has been proved by a preponderance of the evidence against any one of them. Courts sometimes fail to appreciate this issue, and occasionally consciously impose liability under these circumstances to promote separate policy goals.  The latter cases, the subject of the next section of this Part, in fact take the doctrine of res ipsa loquitur well beyond the confines of a rule of circumstantial evidence. They also highlight the fact that res ipsa loquitur, as a rule of circumstantial evidence, simply does not work for the case of the unidentifiable tortfeasor.

In completing this discussion of the circumstantial evidence rule formulation of res ipsa loquitur, it is worth noting the treatment of Wigmore’s statement concerning the rule’s relationship to the defendant’s accessibility to the chief evidence of the case. Although some California cases have considered the “superior knowledge” of the defendant,  this superior knowledge has been held not to be a prerequisite for the doctrine’s application. Prosser, moreover, considered the superior knowledge argument a makeweight which accomplishes nothing but to make the basis for decisions less clear. For res ipsa loquitur as a circumstantial evidence rule, this result is correct. Although nonproduction of important evidence which should have been available may affect the evaluation of the probabilities of the defendant’s negligence, this does not, for the simple purpose of deciding circumstantial evidence cases, require a formal burden-shifting doctrine. The defendant’s presumably superior access to relevant information, however, serves as the foundation for the policy-driven version of res ipsa loquitur.

B. Enhanced Res Ipsa Loquitur

Courts have, in a group of cases, relied upon the defendant’s presumably superior access to relevant information to shift the burden of producing evidence (if not the burden of proof) to the defendant. Although decided in the name of res ipsa loquitur, such cases in reality evidence a departure from the use of the doctrine as a measure of the inferences permissible from the evidence presented in pursuit of policy goals. I will refer to this policy-driven version of res ipsa loquitur as “enhanced res ipsa loquitur” to differentiate it from the circumstantial evidence rule. Enhanced res ipsa loquitur appears in two categories of cases. The first consists of cases in which a special relationship exists between the plaintiff and the defendant, and the courts have employed the doctrine to ensure that in the event of uncertainty the loss falls on the defendant. The second category consists of cases in which a special relationship may exist, but the doctrine is primarily used to sanction the defendant for the nonavailability of evidence.

Enhanced res ipsa loquitur first appeared in cases involving suits by passengers against common carriers. Housel v. Pacific Electric Railway Co., involved a collision on the streets of Los Angeles between a hay wagon and a street car bearing the plaintiff as a passenger. The California Supreme Court interpreted res ipsa loquitur, when applied to common carrier cases, as providing “that proof of the injury to the passenger while he was being carried as such creates a prima facie case or presumption of negligence on the part of the carrier, which the carrier is called upon to meet or rebut.” The court reasoned that in view of the high degree of care required of a carrier toward its passengers, “a collision would not happen in the ordinary course of events if the carrier exercised such care …. ” The court also noted that “the means of proving the specific facts as to the cause of the accident are peculiarly within the power of the carrier, and the explanation should come from it, rather than from the passenger, who very often is unable to ascertain and prove the real facts.” In Bourguignon v. Peninsular Railway Co., the “rule” was reduced to the following formula:

Where the accident is of such a character that it speaks for itself… and raises a presumption of negligence, the defendant will not be held blameless except upon a showing either

  1. of a satisfactory explanation of the accident, that is, an affirmative showing of a definite cause for the accident in which cause no element of negligence on the part of the defendant inheres,
  2. or of such care in all possible respects as necessarily to lead to the conclusion that the accident could not have happened from want of care, but must have been due to some unpreventable cause, although the exact cause is unknown.

The effect is to shift the burden of proof, and the loss if proof is unavailable, to the carrier.

The California Supreme Court later employed enhanced res ipsa loquitur as a products liability precursor in cases involving broken or exploded beverage bottles. In these pre-strict liability cases, to recover from bottlers plaintiffs were required to show either negligence in the bottling process or a defective bottle coupled with negligent inspection for defects by the bottler. The plaintiffs offered no specific evidence of either and the question presented was whether res ipsa loquitur could be used against the defendants. Much of the court’s opinion in each case is spent resolving the question of whether the defendant had sufficient “control” over the bottle in question at the time of the accident for the application of the doctrine, but more important for present purposes are the court’s discussions of the permissibility of inferring the defendant’s negligence from the fact that the bottles broke.

The issue was first debated in Honea v. City Dairy, a case concerning a young girl injured by a milk bottle which “just broke” while she was carrying it. The majority concluded that the court could not take judicial notice “that defects in glass bottles will not ordinarily occur unless the bottler is negligent,” and consequently disallowed application of the doctrine. The dissent argued:

  1. bottles do not ordinarily break unless they are defective;
  2. the bottler had a duty to inspect the bottle and discover any defects;
  3. and based upon evidence that “a defect would be discoverable by reasonable inspection,” failure to inspect or negligent inspection may be inferred from the fact that the defect was not discovered.

In Escola v. Coca Cola Bottling Co.,  a case involving a waitress injured by an exploding Coca Cola bottle, the court noted testimony concerning bottle testing practices and essentially followed the reasoning of the Honea dissent.

The cases use the language of res ipsa loquitur, but in fact much more is going on. A rule that, because practicable tests are available, any failure to detect a defect may be presumed negligent puts the bottler in a very disadvantageous position. There is no cost-benefit analysis of available tests, and even if a bottler performs complete testing, if in some instances the tests are not accurate the bottler would still be liable. As Justice Traynor noted in his Escola concurrence, the result is close to a rule of strict liability. The court used res ipsa loquitur to promote a policy of shifting defective product losses from consumer to producer.

The most prominent cases in which enhanced res ipsa loquitur has been used to sanction the defendants for the nonavailability of evidence are Dierman v. Providence Hospital and Haft v. Lone Palm Hotel. Mabel Dierman was injured during surgery when the electric needle being used to remove a wart from her nose ignited the gas used as an anesthetic.  The explosion could have been caused by the use of an improper gas, gas contaminated by an unclean anesthetizing apparatus, gas contaminated by the hospital or gas contaminated when purchased by the hospital from the manufacturer. The defendant doctor and nurse described the accident and procedures followed but did not offer proof either as to whether the gas was pure or whether they were responsible for its impurity. The jury was instructed on res ipsa loquitur and returned a verdict for the defendants, but the California Supreme Court reversed.

The Dierman case contains elements of a special relationship between defendant and plaintiff and the majority quotes the Bourguignon formula, but California courts in general have not imposed a duty upon physicians and hospitals above a simple negligence standard. The most noteworthy element of the majority opinion, however, is an extended criticism of the defendants’ failure to produce the tank of gas used, a chemical analysis of its contents, evidence of the condition of the tank or the circumstances under which it was stored. The court concluded:

In a res ipsa loquitur case where, in addition to the prima facie showing of negligence, it is admitted or appears beyond dispute that the defendant has it in his power to produce substantial evidence material to the issue but fails to do so, it must be presumed that such evidence, if produced, would have been adverse to defendant, and under such circumstances the evidence is insufficient to support a verdict for the defendant and plaintiff is entitled to a directed verdict.

Because, as Justice Traynor noted in dissent, the relevant time for testing the content of the gas container was the time of the accident and not the time of the trial, the majority’s approach attacks more than a failure to produce available evidence at trial; rather, the majority believed such evidence should have been available and sanctioned the defendants for its nonavailability.

Haft involved the drowning of Morris Haft and his five-year-old son in a motel pool in Palm Springs. In contravention of a state statute, the motel had neither provided a lifeguard nor posted a warning sign at the pool. The court resolved one issue in the case by concluding that the liability of a pool owner who has provided neither a lifeguard nor a warning sign should be measured with respect to the failure to provide a lifeguard. A second issue concerned the burden of proof as to cause-in-fact (i.e., whether the Hafts were responsible for their own drowning). This was also resolved in the plaintiff’s favor. Although the court alluded to the special duty of an innkeeper to his guests,  its principal rationale was that the lack of proof as to causation was a direct and foreseeable result of the defendants’ negligent failure to provide a lifeguard. The court noted that although the main purpose of a lifeguard is to aid those in danger, “an attentive guard does serve the subsidiary function of witnessing those accidents that do occur.”  Because the defendants were responsible for the nonavailability of evidence they were sanctioned with the imposition of the burden of proof. Haft has been followed in multiple collision cases to impose liability upon the defendant responsible for the later collision where that collision made unascertainable the extent of damage caused by the earlier collision.

The enhanced res ipsa loquitur cases, whether special relationship cases or sanction for nonavailability of evidence cases, ignore whether the defendant actually had relevant information that could have been produced at trial. Thus, more is involved than a failure to produce evidence affecting the probability that the defendant was negligent, and the relevance of these cases is not entirely eliminated by modern discovery rules. Rather, enhanced res ipsa loquitur, under the name of res ipsa loquitur and upon a foundation of “superior access to information,” represents a new rule of liability: If evidence is not available and either the defendant has a special relationship with the plaintiff or the defendant is responsible for the nonavailability of evidence, the defendant is liable.

Unlike res ipsa loquitur in the ordinary sense, enhanced res ipsa loquitur may be employed with substantial impact in unidentifiable tortfeasor cases. The leading example of this is Ybarra v. Spangard. The facts of Ybarra are sketchy but simple. Joseph Ybarra entered the hospital for surgery and subsequently developed paralysis and atrophy in his shoulder. Evidence was introduced to the effect that Ybarra’s condition resulted from pressure or strain applied between his shoulder and neck and could have occurred during surgery. The defendants included most of the doctors and nurses who attended Ybarra during his hospital stay and were related (as employees or independent contractors) in a variety of ways which would not normally make any one of them responsible for the conduct of all of the others.

The court’s opinion, although brief, is wide-ranging and speaks to the issues at hand in a variety of voices. The Ybarra decision can be attributed to the defendants’ superior access to relevant information and categorized either as a special duty case or as a sanction for nonavailability of evidence case. There is also a strong element of common enterprise or joint tortfeasor treatment. Finally, the case can be seen as a unique, resultoriented decision.

Ybarra is best viewed, however, as an early example of California courts’ willingness to stretch existing theories and to devise new tort doctrines to aid worthy plaintiffs in unidentifiable tortfeasor cases. Ybarra broke new ground. None of the strands discussed was enough by itself to support a decision for the plaintiff, but taken together they provided a basis to grant relief. The Ybarra “holding” has been followed to varying extents in subsequent cases involving operating room mishaps, but, of greater importance, the Ybarra result has been referred to appiovingly in doctrine expanding cases such as Haft,, Summers v. Tice and Sindell v. Abbott Laboratories. Enhanced res ipsa loquitur as used in Ybarra is a forerunner of express theories of liability designed to address the unidentifiable tortfeasor problem.

C. The Concerted Action and Alternative Liability Theories of Liability

Enhanced res ipsa loquitur is a new theory of liability under the guise of allocating burdens of proof. The next stage in the doctrinal progression was the development of two express theories of liability suitable for application in unidentifiable tortfeasor cases: the concerted action theory and the alternative liability theory. Concerted action and alternative liability are similar in that both involve defendants taking complementary actions and the doctrines are often called into play in comparable factual situations. Their theoretical underpinnings, however, are quite different.

Concerted action is a joint tortfeasor doctrine. As described by Prosser and Keeton, the doctrine provides that joint liability is imposed upon “all those who, in pursuance of a common plan or design to commit a tortious act, actively take part in it, or further it by cooperation or request, or who lend aid or encouragement to the wrongdoer, or ratify and adopt the wrongdoer’s acts done for their benefit.” An express agreement among the defendants is not necessary and a tacit understanding will suffice, but it is “essential that each particular defendant who is to be charged with responsibility shall be proceeding tortiously, which is to say with the intent requisite to committing a tort, or with negligence.” The classic example of the concerted action theory is the case of an unlawful car race between A and B which results in a collision between B’s car and a car driven by C. Under the concerted action theory, A and B are engaged in a common tortious enterprise and C may maintain an action against A even though their cars did not touch.

The leading California concerted action case dealing with the unidentifiable tortfeasor problem is Orser v. George. Orser arose from an accidental shooting at a duck club outing. Vierra, Jacobson and James negligently fired a number of shots at a mudhen. Orser, who was working in a field and in the line of fire, was killed by a pistol bullet. Vierra (and possibly Jacobson) fired the fatal pistol and James fired a rifle. The court found that James must nevertheless be held as a defendant because:

the record of James firing alternately with Vierra at the same mudhen and in the same line of fire] permits a possibility James knew Vierra’s conduct constituted a breach of duty owed Orser and that James was giving Vierra substantial “assistance or encouragement”; also that this was substantial assistance to Vierra in a tortious result with James own conduct, “separately considered, constituting a breach of duty to” Orser.

Once concerted action is shown, particular causation is irrelevant and the problem of identifying the particular agent of causation is solved: All defendants participating in the common enterprise are responsible for the plaintiff’s harm. The challenge lies in determining whether the conduct by the defendants in a particular instance constitutes tortious “concerted action.” Express agreements with respect to tortious enterprises are not common and are in any event difficult to prove. Determining whether the course of conduct undertaken by the defendants evidences an implied understanding, on the other hand, requires difficult line drawing

These difficulties are illustrated by Hall v. E.I. DuPont de Nemours & Co., a federal district court case suggesting a variant on the concerted action theory sometimes referred to as “enterprise liability.” Hall involved a lawsuit against all six American manufacturers of dynamite blasting caps. The plaintiff children were injured while playing with blasting caps which, contained no warning label and could be easily detonated; individual manufacturers of specific caps could not be identified.” The court found sufficient allegations of joint control of risk on the part of the defendants through common adherence to industry safety standards and delegation of functions of safety investigation and design to a jointly sponsored trade association.” The result may very well have differed, however, depending upon factors such as the structure of the industry, the product, the alleged defect and the use made of the trade association. In industrial unidentifiable tortfeasor cases, the application of concerted action theory principles is far from simple.

The case establishing the alternative liability theory is Summers v. Tice. Summers, Tice and Simonson went quail hunting and, despite admonitions to “keep in line,” the hunters ended up being positioned at the points of a triangle.” Tice and Simonson each shot at a quail and one shot, from either Tice’s or Simonson’s gun, hit Summers in the eye. The trial court found that both Tice and Simonson were negligent in firing in Summers’ direction and that Summers was not contributorily negligent.

In considering the case, the California Supreme Court had before it two Mississippi precedents in which two persons had fired shots simultaneously but only one, who could not be identified, had hit another person. Oliver v. Miles, involving two hunters who negligently fired across a road and hit a passerby, and Moore v. Foster, involving two policemen who wrongfully fired at a fleeing suspect, had each been resolved on the theory that the defendants’ activity constituted concerted action. In Summers, however, the court did not rely on the concerted action theory, perhaps because the plaintiff had neglected to proceed on that theory at the trial court level. Instead, the court reasoned that because the defendants were both wrongdoers and created the situation where the negligence of one of them injured the plaintiff, the burden should rest with each defendant to absolve himself or be jointly liable for the whole damages.  Like enhanced res ipsa loquitur, Summers has been applied in multiple collision cases.  In general, however, incidents of contemporaneous negligence by two or more defendants resulting in an untraceable injury have apparently been rare and the Summers rule has not often been found controlling.

The concerted action theory, as a theoretical matter, fits neatly into the category of joint torts, the concerted action of the defendants constituting a central element of the tort. The alternative liability theory is quite different. Whether expressed in terms of a mere projection of proper behavioral norms or unfair liability for at least one defendant for an injury he did not cause, Summers represents the imposition of liability for negligent risk creation and represents a major departure from traditional principles of tort law. In allocating the burden of loss between an innocent plaintiff and negligent defendants, Summers comes very close to endorsing the concept of negligence in the air.

Notwithstanding their differences, the concerted action and alternative liability theories have each provided an express doctrine for dealing with unidentifiable tortfeasor cases. By admitting the formulation of independent theories of liability, each moves beyond the groping of Ybarra to a rulesystem by. which liability may be determined. These theories of liability provide the principal backdrop for the most challenging unidentifiable tortfeasor cases presented to date-those involving lawsuits by women injured in utero by DES.


A. The Market Share Answer to the DES Causation Problem

The unidentifiable tortfeasor issue has been brought to the fore in the last several years with the emergence of claims against the manufacturers of the drug diethylstilbestrol (DES) and the landmark California Supreme Court decision in Sindell v. Abbott Laboratories. DES is a synthetic estrogenic hormone first synthesized by a group of British medical researchers in the late 1930s. A number of drug companies thereafter filed New Drug Applications (NDAs) with the Federal Food and Drug Administration (FDA) requesting authorization to produce and market DES for several purposes, none related to problems in pregnancy. Following an FDA request for information pooling in late 1940, several drug companies formed a “small committee” to coordinate the joint submission of clinical data on DES in a “master file” to be used with respect to all DES NDAs. The FDA approved the marketing of DES for nonpregnancy uses in late 1941. Supplemental NDAs for the use of DES as a miscarriage preventative were filed in 1947. A few companies conducted experiments on the safety and efficacy of DES for this purpose, but most relied instead upon published studies done by independent researchers at several medical schools. The FDA approved the marketing of DES as a miscarriage preventative in July 1947. Following a study linking a form of cancer in young women with the use of DES by their mothers during pregnancy, the FDA contraindicated DES for use for the prevention of miscarriages in November 1971.

Although there were apparently a few principal producers, 34 as many as 200 to 300 companies manufactured and marketed DES between 1947 and 1971. As described by one court:

Some companies marketed the drug under a trade name; others marketed it generically. Several companies supplied DES to competitors. Because the DES compounds produced by the drug companies were chemically identical, pharmacists often filled prescriptions for DES with whatever company’s drug was in stock, a practice that the firms were aware of. None of the companies warned physicians about the possibility of carcinogenic or other risks to the offspring of women who took DES.

In fact, a number of the daughters of women who ingested DES during pregnancy have suffered clear cell adenocarcinoma, a fast-spreading vaginal and cervical cancer requiring radical surgery, and many more have suffered adenosis, a vaginal tract abnormality of uncertain import. Clear cell adenocarcinoma is extremely rare outside of the DES context and has a minimum latent period of ten to twelve years. Plaintiffs allege that drug companies did inadequate testing, knew or should have known that DES was unsafe and failed to give adequate warnings of its potential danger.

A significant difficulty facing DES plaintiffs has been an inability to identify any particular drug company as the producer of the DES ingested by their mothers. The DES problem is widespread with numerous actors (both drug companies and victims) and no unity of time or place, either with respect to the tortious acts performed or the injuries incurred. The difficulty in identifying particular tortfeasors results from both the time past and the indistinct marketing of DES. Memories have faded and records have been lost or destroyed and there were many manufacturers of a relatively fungible product. Although plaintiffs have asserted that the drug companies should bear the responsibility for the generic use of the drug and defendants have countered that the plaintiffs’ mothers had better access to their particular prescription information, plaintiffs’ inability to identify particular tortfeasors cannot be squarely blamed on either party. As one commentator has observed, the DES cases may be one of the rare instances “in which useful, nonquantitative evidence is all but impossible to obtain.”

The Sindell case was brought against eleven drug manufacturers by Judith Sindell, a DES daughter who suffered a malignant bladder tumor and adenosis. The suit was brought as a class action requesting compensatory and punitive damages for Sindell and equitable relief for the class. Sindell pleaded a number of theories of liability and alleged concerted action and a joint enterprise on the part of the defendants in an effort to make them jointly liable. Sindell acknowledged that she could not identify the manufacturer of the particular DES taken by her mother. The trial court dismissed the action on the basis of Sindell’s inability to identify a particular manufacturer, but the court of appeal reversed, holding that the plaintiff could proceed on both the concerted action and alternative liability theories of liability.

The California Supreme Court also reversed the trial court, but not for the reasons articulated by the court of appeal. The California Supreme Court rejected concerted action, alternative liability and other unidentifiable tortfeasor theories of liability  but instead fashioned a new theory of liability known as “market share liability.” The market share liability rule generally works as follows:

  1. If the plaintiff is innocent,
  2. the defendants are negligent (at least in general terms),
  3. the plaintiff’s injury was caused by a uniform product,
  4. the plaintiff, through no fault of her own, cannot identify the particular manufacturer responsible for her harm
  5. and the plaintiff has joined as defendants the manufacturers of a substantial share of the product that caused her injury,

then the burden shifts to each defendant to either demonstrate that it could not have made the particular product that caused the plaintiff’s injury or assume liability for the plaintiff’s loss in proportion to its market share.

The court elected to devise a remedy because, as between an innocent plaintiff and negligent defendants, the latter should bear the cost of the injury. The court also reasoned that in “our contemporary complex industrialized society, advances in science and technology create fungible goods which may harm consumers and which cannot be traced to any specific producer” and courts should fashion remedies to meet changing needs, just as courts created strict products liability to adapt to “an era of mass production and complex marketing methods.” In the DES context, the court found it reasonable to measure the likelihood that any of the defendants produced the actual injury-causing product “by the percentage which the DES sold by each of them for the purpose of preventing miscarriage bears to the entire production of the drug sold by all for that purpose.”

B. Sindell’s Unanswered Questions

In establishing market share liability in Sindell, the California Supreme Court left open a number of important questions relating to the doctrine’s application, only some of which have been addressed in subsequent DES cases. The first of these questions concerns the standard of care required of DES manufacturers and the related issue of which specific causes of action can be pursued on a market share theory when a particular responsible defendant is unidentifiable. In Sindell, the plaintiff pleaded a number of causes of action and requested punitive damages. Although the majority opinion in Sindell uses the language of negligence, the court did not address specifically the standard of care to be applied.

Most of the cause of action/market share questions were addressed directly in the California Supreme Court’s recent decision in Brown v. Superior Court of San Francisco. Brown involved at least sixty-nine individual DES cases that were consolidated for the purpose of deciding common legal questions. On appeal from pretrial rulings adverse to the plaintiffs, the court decided that drug manufacturers could not be held strictly liable for a defect in the design of a prescription drug. That determination was not based on the market share theory, but on “the public interest in the development, availability and reasonable price of drugs.”

The court also determined that neither a breach of express or implied warranty claim nor a fraud claim could be pursued on a market share theory, the former because recovery on a warranty theory would be inconsistent with the court’s resolution of the strict liability question, and the latter because an essential element of a fraud claim is the state of mind of a particular manufacturer, a showing too individualized to resolve on a market share basis. Although the punitive damages issue was not addressed in Brown, the court’s fraud analysis suggests that punitive damages cannot be recovered under a market share theory.

It is also worth noting that arguments more relevant to the standard of care question can easily enter the debate on the merits of the market share theory. This is the case in both the majority and dissenting opinions in Sindell, the majority characterizing the defendants as better cost spreaders and the dissent charging that market share liability will inevitably inhibit the dissemination of new drugs. The Brown decision will, one hopes, serve as a focal point for the standard of care debate and allow market share liability to be analyzed on its merits as an unidentifiable tortfeasor doctrine.

A second question left open by Sindell but resolved by Brown is whether, under a market share theory, the defendants before the court are jointly liable for all of the plaintiff’s losses (with the defendants’ market shares being used simply to apportion damages among the defendants) or whether the defendants are only severally liable for a percentage of the plaintiff’s losses equal to each defendant’s market share. Viewed another way, do the defendants (through higher payments) or the plaintiff (through a less than full recovery) absorb a loss for the market share of manufacturers who are out of business, bankrupt, not amenable to service of process or otherwise not joined as defendants in the action?

The majority opinion in Sindell can be read either way. The opinion refers to apportioning damages among the defendants, states that the defendants may cross-complain against other DES manufacturers and confesses that “a defendant may be held liable for a somewhat different percentage of the damage than its share of the appropriate market would justify.” On the other hand, the opinion asserts that each defendant will only be liable for the proportion of the judgment represented by its share of the market, manufacturers will not be held responsible for the products of another and “each manufacturer’s liability for an injury would be approximately equivalent to the damages caused by the DES it manufactured.” Most commentators have read Sindell as imposing only several liability, but others, including the Sindell dissent, have read Sindell to impose liability for 100% of the plaintiff’s damages. Of the three other state supreme courts adopting a market share type theory, one opted for a variant on joint liability,’ one opted for several liability and the third took an intermediate course.

In Brown, the California Supreme Court rejected the joint liability interpretation and concluded that, under a market share theory, each defendant should be liable only for the portion of a plaintiff’s damages that corresponds to the percentage of its share of the relevant market for DES. The court recognized that joint liability may subject a defendant to a portion of the judgment greatly in excess of its market share and that several liability would likely result in a less than full recovery for the plaintiff. The court’s choice of several liability was in large measure determined by “Sindell’s goal of achieving a balance between the interests of DES plaintiffs and manufacturers of the drug.

A rule of several liability, however, has more to commend it than simply being a good compromise between leaving plaintiffs remediless and subjecting defendants to damages in excess of their share. Several liability is more consistent with Sindell’s stated goal of reproducing what would occur if identification were possible in all cases. Also, if market share liability is to be championed as a doctrine imposing liability for risk creation, as opposed to merely dividing a loss between plaintiffs and defendants, the risk created by a particular drug company is not higher because not all manufacturers can be joined in an action. Also, economic efficiency considerations suggest that to force defendants to internalize losses properly attributable to the production (market share) of other drug manufacturers may result in overdeterrence of drug production. Finally, in breaking new legal ground to devise a remedy benefiting plaintiffs it is important institutionally for a court to at least appear to be treating defendants fairly.

Another limitation on plaintiffs’ ability to recover under a market share theory not fully articulated in Sindell is the requirement that the plaintiff join as defendants drug manufacturers whose market shares represent a “substantial share” of the DES market. The court noted that a law review note advocating a theory akin to market share liability suggested that 75- 80% of the DES market should be required but the court declined to establish a specific percentage as a threshold.

An opportunity to articulate the substantial share requirement more specifically was presented in Murphy v. E.R. Squibb & Sons. Murphy was brought by Christine Murphy, an individual DES daughter, against a single drug manufacturer, E.R. Squibb & Sons, Inc., on the theory that Squibb produced the particular DES taken by her mother. After the Sindell decision was announced, Murphy attempted to broaden her action against Squibb to include a market share theory and offered to prove that Squibb had a ten percent share of the national market for DES. The trial court only allowed Murphy to proceed on her original theory and the jury returned a special verdict finding that the DES purchased by Murphy’s mother was not manufactured by Squibb. The court of appeal affirmed on the theory that the special verdict established a market share theory defense by satisfying Squibb’s burden of proving that it did not manufacture the injury-causing DES. The California Supreme Court also affirmed the trial court,  but on a different ground, holding that ten percent of the DES market did not constitute a “substantial share.”

The court again left open, however, the percentage of the market it would consider a “substantial share.” Of more fundamental concern is whether the “substantial share” requirement is valuable at all. The California Supreme Court’s stated reason for the substantial share requirement was “to diminish the injustice of shifting the burden of proof to defendants to demonstrate that they could not have made the drug which caused the plaintiff’s injuries.” The court also appears to have been trying to minimize the extent to which market share liability departed from the alternative liability theory of Summers, which the court interpreted as requiring all possible tortfeasors to be before the court. If defendants were jointly liable under a market share theory for all of the plaintiff’s damages, a substantial share requirement would serve to reduce defendants’ exposure to overpayment.  With several liability, however, defendants are not exposed to overpayment. Moreover, the likelihood of any individual drug manufacturer being held liable for a portion of a judgment when it in fact did not cause the plaintiff’s injury is not affected by the presence of other defendants. This has led some to argue that the substantial share requirement is unnecessary.

The substantial share requirement is helpful, however, insofar as it serves as a forced joinder rule and an election of legal theory rule. Forcing a plaintiff to join a number of drug manufacturers in her market share suit can promote fairness in several ways. With more manufacturers participating in the action, better data on market shares is likely to be available. In addition, multiple defendants can spread legal costs, at least as to common issues. Plaintiffs also will not be able to force settlements on individual defendants with a small market share who face slight liability but for whom the cost of defending a suit would be burdensome, which also may decrease the number of suits filed.

The way the substantial share requirement acts as an election of legal theory rule is illustrated by the facts of Murphy. For Murphy to have proceeded on her traditional action against Squibb while at the same time joining a number of manufacturers and proceeding on a market share theory would have been awkward at best. By essentially forcing the plaintiff to choose between a traditional action against a single drug company and a market share suit, the substantial share requirement protects courts from having to handle two trials at once, and to the extent plaintiffs choose to proceed against a single manufacturer, the number of market share suits would decrease. Although the substantial share requirement denies plaintiffs like Murphy who try and fail to identify a particular manufacturer even a partial recovery, this disadvantage is outweighed by administrative advantages for the court.

An even more important issue with market share liability is the relevant definition of the market. The definition may (or may not) take into account a variety of factors, including time periods, geographic areas, product identifiability and marketing approaches. Manufacturers entered and left the DES market throughout the twenty-four year period during which DES was marketed as a miscarriage preventative, so DES market shares differed at different times. Also, national market shares differed from local market shares and information on both is sketchy. Neither national nor local market shares necessarily correspond to the amount of DES sold by a particular pharmacy. Although DES was manufactured using a standard scientific formula, pills differed, at least to some extent, in dosage, size, shape and color. Also, the marketing schemes employed by manufacturers differed, some using brand names, others selling generically, and with variations in price and perhaps record keeping and distribution schemes.

One approach is to define market share narrowly, focusing on the particular facts of the individual case at hand. Even if unable to identify a manufacturer, plaintiffs should at least be able to identify the time and place of pregnancy and may be able to provide some description of the injury-causing product. Market share could be determined with respect to the DES sold during a particular time period, in a particular pharmacy or city and/or with particular physical characteristics. The principal advantage of this approach is that if market share is sensitive to the facts before the court, it will most nearly approximate the probability that the defendant’s product caused the plaintiff’s injury. In addition, a tightly focused market share approach ties market share liability more closely to normal tort rules in the event the plaintiff has some information identifying the manufacturer.

An alternate approach is to define the market broadly without regard to the details of a given plaintiff’s situation. Defendants’ “market shares” would be constant from case to case notwithstanding the availability of particularized information affecting the probabilities of causation in a given instance. Even if DES suits are not pursued as class actions, mass-litigation techniques such as those employed in Brown allow parties and courts to benefit from economies of scale in fact-finding through the use of a single set of market share determinations in a number of cases. Over a large run of cases defendants’ liability in the aggregate should work out properly. Also, market share cases should have consistent outcomes.

With either approach “market share” can be refined to reflect not simply gross product sold, but the likelihood of the defendant having manufactured the injury-causing product in an unidentifiable tortfeaser case. Such refinement would attempt to account for variations in the identifiability or harmfulness of defendants’ products. Without such refinement, manufacturers with relatively identifiable products would face greater overall liability in that they would be solely responsible for damages in conventional suits in which they were identified without any reduction of their proportion of market share judgments. Making such adjustments to “market shares,” however, would likely present significant proof problems and would risk adding another level of complication and arbitrariness to already difficult adjudications.

In Sindell, the court defined the market broadly as the “entire production of the drug sold by all manufacturers for the purpose of preventing miscarriage,” but carved out an exclusion from liability for any defendant which can prove that it did not manufacture the injury-causing pills in a particular case. The wisdom of the Sindell approach depends upon the availability and quality of focused or direct evidence. The choice of market share definition inevitably involves a trade off of administrability and consistency versus precision in particular cases. If evidence to refine “market shares” is difficult to obtain or of questionable accuracy, the pursuit of precision may be little more than a costly exercise in arbitrariness. As a first venture into a new area with no way for the court to grasp the full evidentiary picture, Sindell’s broad approach is reasonable. The exclusion for defendants who could not have been responsible, although of little use to most manufacturers, at least minimizes the appearance of gross unfairness in particular cases.

A final issue presented by market share liability involves the cases in which the plaintiff has some information pointing to a particular manufacturer. In Rogers v. Rexall Drug Co., decided with Sindell, the plaintiff amended her complaint to allege that a particular defendant manufactured the DES which injured her. The court suggested that, should she fail to establish that fact, she could rely on a market share theory.

Alternatives are available. For example, suits in which plaintiffs pursue recovery against a particular manufacturer could be disallowed altogether. This would eliminate the costly pursuit of particular evidence and would avoid excess liability for defendants with identifiable products. On the other hand, this approach would deny plaintiffs a remedy under traditional tort theories and might force courts to unnecessarily incur the burdens of handling market share liability cases.

A less drastic alternative would be to deny plaintiffs the opportunity to pursue a market share recovery in cases where it does not seem necessary or appropriate. This would avoid the assertion that market share is a reasonable approximation of the likelihood that a particular manufacturer caused the plaintiff’s injury in the face of a significant amount of specific evidence, but might place plaintiffs with no specific evidence in a relatively better position, perhaps discouraging the production of evidence. As is the case in defining the relevant market, the best approach to these cases may only be determinable as courts gain experience.

The particulars of market share liability remaining unsettled after Brown are noteworthy but are perhaps inevitable with a new theory of liability. Their resolution is not necessary to evaluate the position of market share liability in the panoply of unidentifiable tortfeaser doctrines.

C. Market Share Liability in Perspective

An important aspect of market share liability which has received little attention from commentators is what the Sindell court could have done but did not do. Faced with the Sindell appeal and the set of facts pleaded, the California Supreme Court could have chosen any of three different courses of action:

  1. affirm the trial court and deny recovery to the plaintiff,
  2. conclude that the facts pleaded by the plaintiff stated a cause of action under recognized theories of liability for unidentifiable tortfeasor cases,
  3. or devise a new theory of liability (or make explicit modifications to an existing theory) to provide the plaintiff a remedy.

In addition to the general factors counseling restraint in the creation of new theories of liability,  in the DES context legislative or administrative solutions have considerable appeal. Yet administrative compensation systems are not without problems. Moreover, the legislative process to establish a compensatory scheme would by its nature be political, involving the political power of manufacturers as well as the sympathetic or moral appeal of victims. A premature closing of the courthouse doors would likely disadvantage the DES plaintiffs in that manufacturers would have little incentive to participate in a legislative solution if they no longer feared judicial liability. The DES unidentifiable tortfeasor problem is a tort law problem. Whether they endorse or deny a remedy, courts have an obligation to address the issue.

Unlike other courts,  the Sindell court held that the facts alleged by the plaintiff stated a cause of action. Before articulating its market share theory, however, the court rejected the application of enhanced res ipsa loquitur as embodied in Haft, the concerted action theory of liability and the enterprise liability variation thereof in Hall; and the alternative liability theory. The rejection of these unidentifiable tortfeasor doctrines on the pleaded facts was more than mere table-setting for market share liability. The endorsement of any one of these theories in the DES context would have expanded greatly its scope with significant consequence for future application in other situations.

Sindell argued that Haft was analogous because the “defendants’ failure to discover or warn of the dangers of DES and to label the drug as experimental caused her mother to fail to keep records or remember the brand name of the drug prescribed to her.  The court concluded, however, that the absence of evidence resulted “primarily from the passage of time rather than from the defendants’ acts of failing to provide adequate warnings” and was not “due to the fault of defendants.” The court also noted the “superior access to information” language in Ybarra and Summers but commented that in Sindell neither the plaintiff nor the defendants were in a better position to identify the manufacturer of DES ingested by the plaintiff’s mother.

Following the Haft reasoning to find DES manufacturers liable would have imposed significant record-keeping duties on drug manufacturers, especially given the time element and indirect relationship between manufacturer and user. To hold manufacturers liable for failing to provide labels that would have led to the availability of evidence is to overrun the unidentifiable tortfeasor issue. The failure to label is at the heart of the negligence issue, but does not provide a link between a particular manufacturer and a given plaintiff unless, under enhanced res ipsa loquitur notions, one makes a defendant’s negligence a sufficient reason to decide the identification issue against it as well. To hold negligent defendants automatically liable in an unidentifiable tortfeasor case without regard to their degree of cooperation, their relationship to the plaintiff or their present ability to produce evidence would isolate a single aspect of Ybarra as sufficient to impose liability. This would significantly expand enhanced res ipsa loquitur in the unidentifiable tortfeasor context.

Sindell’s concert of action claim was based upon allegations of

“planned and concerted action, express and implied agreements, collaboration in, reliance upon, acquiescence in and ratification, exploitation and adoption of each other’s testing, marketing methods, lack of warnings … and other acts or omissions.. .” and that “acting individually and in concert, [defendants] promoted, approved, authorized, acquiesced in, and reaped profits from sales” of DES.

These allegations, Sindell claimed, “state a ‘tacit understanding’ among defendants to commit a tortious act against her.”  The court of appeal concluded that Sindell’s allegations suggested that each defendant “gave substantial ‘assistance or encouragement’ to the tortious conduct of the others” and that a concert of action cause of action could be maintained.

The California Supreme Court, however, looked more deeply into the complaint and determined that ” the gravamen of the charge of concert was that defendants failed to adequately test the drug or to give sufficient warnings of its dangers and that they relied upon the tests performed by one another and took advantage of each others’ promotional and marketing techniques . . . which the court viewed as common parallel or imitative conduct. The court reviewed Orser v. George and other cases and characterized concert of action cases as involving a small number of defendants, a single plaintiff, actions occurring over a short span of time and direct participation by the defendant in the injury-causing act or encouragement or assistance of the person who directly caused the injury. The court also concluded that the genericness of the DES manufactured was understandable in the prescription drug context. Finally the court thought it “dubious whether liability on the concert of action theory can be predicated upon substantial assistance and encouragement given … pursuant to a tacit understanding to fail to perform an act.”

The Sindell court correctly perceived that the application of the concert of action theory to allow liability in that case would greatly extend the reach of that doctrine. By limiting the concert of action theory, the court prevented parallel conduct on the part of manufacturers from resulting in joint and several liability for each without regard to whether it produced, or demonstrably did not produce, the injury-causing product.

The Sindell court also rejected the “enterprise liability” variant on the concerted action theory of Hall v. E.I. DuPont de Nemours & Co. Sindell argued that DES manufacturers followed an industry-wide safety standard and pointed ‘to a law review comment detailing an “enterprise liability” approach to the DES causation problem.  The court, however, distinguished Hall because, unlike the blasting cap industry, there were a large number of DES manufacturers and no trade association had been delegated functions related to product safety. Also, FDA regulation resulted in product standards influenced to a considerable degree by the federal government. The court, in essence, took a narrow view of joint control of risk. Although following industry standards should not establish due care per se, neither should it establish liability without evidence of causation.

The most attractive of the existing unidentifiable tortfeasor doctrines before the Sindell court was the alternative liability theory of Summers v. Tice. Like Summers, Sindell can be characterized as a case involving an innocent plaintiff and negligent defendants in which evidence identifying the injury-causing defendant is unavailable through no fault of the plaintiff’s. The court of appeal, drawing on Ybarra and Haft, had found the alternative liability theory applicable.

The California Supreme Court, however, rejected alternative liability. In so doing, the court focused on the fact that, of as many as 200 DES manufacturers, only six were before the court. The court expressed concern that there was therefore a “substantial likelihood” that none of the defendants before the court had manufactured the DES which caused the plaintiff’s injuries. This, however, did not prevent the court from creating market share liability, although the “substantial share” requirement may be seen as an attempt to address the concern. The court’s concern with alternative liability, therefore, appears to have been primarily with imposing joint and several liability on all defendants without regard to the likelihood that a particular defendant produced the injury-causing product. Summers involved two defendants, both before the court, with each equally likely to have caused the plaintiff’s injury, so joint and several liability worked well. The absence of some manufacturers and the varying market shares of those present, however, would make dividing liability equally among those defendants before the court neither efficient nor fair.

In addition, Summers’ transfer of the burden of proof to the defendants to absolve themselves is most reasonable when all who may have caused the injury are before the court. Consider, for example, the facts of Eley v. Curzon. In Eley, a pedestrian on a highway in low visibility conditions was hit by a car or truck. Three drivers who may have hit the plaintiff were named as defendants. However, the plaintiff could have been struck by yet a fourth driver, and without the presence of a party to speak to this possible cause the defendants present would be left to absolve themselves through speculation.  By declining in Sindell to apply unmodified the alternative liability theory, the court contained the theory and prevented its expansion to cases far afield of the Summers scenario.

Market share liability is in some respects a radical theory. Like alternative liability, market share liability imposes liability for risk creation. Market share liability goes further, however, in at least one respect. In Summers the defendants each breached a duty toward a particular plaintiff before the court, but in Sindell defendants breached duties to indeterminate DES daughters whose mothers used their products. Market share liability deals with the identifiable tortfeasor issue in the aggregate, replacing individual responsibility with collective responsibility.

Viewed in perspective, however, market share liability is a narrow unidentifiable tortfeasor doctrine tailored to a particular set of circumstances. As presently articulated, the doctrine does not reach unidentifiable tortfeasor cases involving nonfungible products, cases in which the plaintiff’s injury may not have been wrongfully caused or cases in which not all defendants have acted tortiously. The nonfungibility problem has restricted the use of market share liability in the asbestos context. The non-wrongful cause limitation appears to limit the doctrine’s applicability in cases such as suits against polluters who increase risks of disease. Finally, the non-tortiouslyacting defendants limitation effectively precludes the use of market share liability in manufacturing defect (as opposed to design defect) product liability cases.

Perhaps Sindell’s most significant breakthrough is its demonstration of a court’s willingness to devise new tort doctrines to deal with specific unidentifiable tortfeasor situations. In the next Part of this Article I will suggest certain factors courts should take into account in devising new unidentifiable tortfeasor remedies. Measured by these criteria, market share liability appears to be a well-crafted approach to the DES causation problem.


In Part I of this Article I examined the development of unidentifiable tortfeasor doctrines in a variety of contexts. In Part II, I examined the market share theory of liability and noted that, although market share liability marked a major breakthrough in the DES context, the theory was carefully crafted for the particular unidentifiable tortfeasor problem presented and is more limited than would have been the endorsement of the application of existing unidentifiable tortfeasor doctrines.

In this Part, I will discuss several interrelated categories of issues courts should consider in devising new unidentifiable tortfeasor doctrines or expanding existing doctrines. These categories can be loosely labeled evidence production considerations, effectiveness considerations, the moral imperative and institutional considerations. These will be considered in the light of two unidentifiable tortfeasor settings: the DES situation and the situation presented by the well-known “blue bus” hypothetical. The DES situation has been described earlier. The “blue bus” hypothetical can be stated as follows:

Mrs. Smith was driving on a public street and was forced off the road by a negligently driven bus. She is able to testify that the bus was blue, but is unable to describe the bus to any greater extent. Blue Bus Co. owns and operates 80% of the blue buses operating in the town. Mrs. Smith files a negligence action against Blue Bus Co. alleging the foregoing. Does she recover?

A. Evidence Production Considerations

The benefits for dispute resolution of having relatively full evidence before the court are plain. Fact-finding will be more accurate and judgments perceived to be based upon complete information will likely be accorded greater public acceptance. The evidence production question, therefore, is not whether additional evidence is beneficial but instead how far to pursue its production.

The question has two separate aspects. The first concerns incentives to produce available evidence in a given case. Evidence production can be encouraged by placing the burden on the party expected to be able to produce evidence to produce it or lose, even though evidence before the court suggests that that party should win.  Ybarra. reflects this concern in part.

The other aspect concerns incentives to obtain or preserve evidence in a particular category of cases. Assuming important evidence is not presently available, the responsible party can be held accountable, thereby providing incentives for labelling, record keeping and witnessing. This was the main thrust of the version of enhanced res ipsa loquitur propounded in Dierman and Haft.

In Sindell neither party could be expected to produce evidence as to specific causation and the lack of evidence could not fairly be attributed to the conduct of either the plaintiff or the defendants. In the blue bus case, however, evidence suppression is an important issue. Under most circumstances a driver run off the road by a bus would be able to make a more complete identification than simply that the bus was blue. Before providing Mrs. Smith a remedy, the court must be comfortable with her explanation of her inability to provide a better description. To award Mrs. Smith a recovery would otherwise create a disincentive for her to provide evidence. Evidence obtainment and preservation concerns are less salient but could be relevant if Mrs. Smith did not keep her spectacles prescription current or if Blue Bus Co.’s practices made its buses difficult to identify.

The pursuit of evidence can, of course, be taken too far28s and courts must be careful to avoid making, to quote Prosser, “sheer ignorance … the most powerful weapon in law.  Nevertheless, before fashioning or extending unidentifiable tortfeasor doctrines courts must be sensitive to the effects of such doctrines on incentives to produce, obtain and preserve relevant evidence.

B. Effectiveness Considerations

Effectiveness considerations involve the effectiveness of an unidentifiable tortfeasor doctrine in achieving the optimum distribution of loss between plaintiffs and defendants and among defendants. An effective remedy avoids overdeterrence and underdeterrence and leaves each party in a fair position. Effectiveness concerns are most significant with unidentifiable tortfeasor doctrines employing probabilistic or statistical evidence. One’ aspect of the problem concerns the efficiency of a remedy in a particular case or category of cases and another concerns the flexibility of the jurisdiction’s tort system.

Before devising or employing an unidentifiable tortfeasor doctrine based upon probabilistic or statistical evidence, courts must first consider the probative value of such evidence. If much specific evidence relating to the factual determinations to be made is before the court, probabilistic or statistical evidence may be of very little help. If specific evidence is not available, courts must, before employing probabilistic or statistical evidence, ascertain the closeness of the relationship between the measure employed and the determination sought. The value of background statistics can vary significantly.

In the DES context, although market shares are difficult to determine and the market share theory does not account for possible differences in the harmfulness of DES produced, the amount of DES produced by each drug manufacturer is a reasonable approximation of the amount of harm caused.

A close relationship between market shares and harm caused often does not exist, however, in many other cases which appear similar. Some products, like asbestos, appear in a variety of forms with varying toxicities. Some products, like cigarettes,  increase the risk of certain types of diseases without being the sole cause. Also, differences in marketing methods and the presence or absence of warnings and safety instructions may make equally dangerous products differ in their likelihood of causing injury. In such cases “market shares” alone are not sufficient, and reasonable causation probabilities can only be determined with difficulty and a fair degree of speculation.

In the blue bus case, it does not necessarily follow from the fact that Blue Bus Co. owns and operates 80% of the blue buses operating in the town that there is an 80% likelihood that Blue Bus Co. caused Mrs. Smith’s accident. Probabilities would differ if Blue Bus Co.’s drivers drove negligently more (or less) often than drivers of other companies294 and could change dramatically if the accident occurred on a regular route of Blue Bus Co. (or another bus company) or if the accident occurred near (or away from) Blue Bus Co.’s yard.

A more general consideration in devising probability-based unidentifiable tortfeasor doctrines is whether the jurisdiction’s tort rules are sufficiently flexible to apportion liability fairly. With market share liability, as amplified by Brown, DES manufacturers are liable only severally and in a proportion not in excess of their market shares. If the plaintiff cannot be limited to less than a full recovery or if the defendants’ liability must be joint and several, however, solvent defendants before the court may be subject to greater than “efficient” liability. In the blue bus case, for example, Blue Bus Co. may face liability for all accidents involving unidentified blue buses.

C. The Moral Imperative

The moral imperative supports applying an unidentifiable tortfeasor doctrine when it can be shown independently of the specific causation issue that the defendants each breached a duty of care owed to the plaintiff or similarly situated persons. In the DES situation presented in Sindell, all defendants were assumed to have been negligent and a cornerstone of the court’s decision was the rationale of Summers v. Tice that “as between an innocent plaintiff and negligent defendants, the latter should bear the cost of the injury.” Even if, as the Sindell dissent pointed out, it is more likely than not that a given defendant did not cause the injury of the particular plaintiff, each DES manufacturer did increase the risk of injury to the plaintiff and other DES daughters collectively and it is likely that each defendant’s wrongful conduct was responsible for harm to someone.

When, in an unidentifiable tortfeasor situation, causation and negligence are linked, however, uncertainty about identity is also uncertainty about negligence. In the blue bus case, for example, if Blue Bus Co. did not force Mrs. Smith’s car off the road, Blue Bus Co. did not act negligently toward anyone. If we believe there is an 80% chance Blue Bus Co. caused Mrs. Smith’s accident and Mrs. Smith is allowed to prevail, there is an 80% chance of having correctly held liable a tortfeasor. If, however, ten separate bus companies each operate 10% of the blue buses operating in the town, to award a remedy would impose liability on ten defendants each of which was substantially less likely than not negligent and nine of which were in fact innocent. The moral imperative for providing a remedy in such a case is at best weak and the message delivered by the court is more “don’t operate buses” than “don’t act wrongfully.

Unidentifiable tortfeasor cases involving manufacturing defects are similar. In Sheffield v. Eli Lilly & Co., for example, the plaintiff had been permanently disabled by an injection of defective Salk polio vaccine, the manufacturer of which could no longer be identified. A critical difference from Sindell was that all defendants in Sindell manufactured a defective generic product, while in Sheffield, although all defendants manufactured a generic product, only one manufactured a defective one and market share liability was rejected. Courts must be wary, therefore, of employing unidentifiable tortfeasor doctrines in cases involving isolated injuries or other situations in which an independent showing cannot be made on the standard of care issue.

D. Institutional Considerations

Before devising new unidentifiable tortfeasor doctrines or employing existing doctrines in new situations, courts must consider issues relating to the role and operations of the judicial system. A readily apparent issue concerns the role of the courts in addressing the existing harm. Legislative solutions are not always feasible and the denial or grant of a tort remedy may affect the legislative process. Nevertheless, many situations are better left in the legislative domain and/or are best addressed by providing administrative remedies.

A more subtle factor involves the public acceptance of judgments. A goal of the judicial process is to articulate statements about past events that can be accepted as true for purposes of entering a judgment and spelling out the rights of the parties thereafter. A problem for the acceptability of unidentifiable tortfeasor doctrines based primarily on statistical evidence is that uncertainty is acknowledged and the public is aware that the trier of fact cannot do better than make a probabilistic statement, a “bet.” Against this, of course, must be balanced public acceptance difficulties in withholding a remedy from deserving plaintiffs 0 and the value to the judicial system of being seen as attempting to reach probable results, thereby reducing the number of “errors.” There are a large number of DES cases and liability may be viewed as working out in the aggregate. Acceptability is a significant concern, however, in isolated incident cases.

A third institutional consideration is the wise allocation of judicial resources. Ideally, no proper remedy should be denied because of inadequate resources. Realistically, courts have limited resources which they should allocate in a manner maximizing the judicial system’s productivity. Even assuming accurate results are obtainable, overcoming formidable proof problems may be difficult and resource consuming. The DES situation involves a large number of cases and a great deal of harm. Providing a remedy for isolated incidents like the blue bus case, however, may not be worthwhile. To ensure that limited judicial resources are well spent, before devising or employing new unidentifiable tortfeasor doctrines courts must balance the magnitude of the problem presented, in terms of the number of like cases and the severity of harm caused, against administrative burdens and proof problems.

The practical realities of litigation also burden the parties so courts should evaluate the magnitude of the harm and the problem of proof from the litigants’ perspective. Granting a remedy while placing a virtually insurmountable burden of proof upon the plaintiff does not accomplish much. Conversely, placing heavy or impossible proof burdens on defendants may make suits difficult to defend from a practical standpoint and amount to an imposition of liability. A situation of particular concern would be one in which a plaintiff could maintain an action against a number of defendants with bare allegations or only a minimal factual showing. In such a case it may be cost-effective for a plaintiff to bring suit but not cost-effective to present even a meritorious defense, especially if a defendant’s share of the total liability is minor. Thus, the plaintiff may be able to readily obtain settlements without the need to have, or to establish, a case.

Finally, courts must consider the possibility that a new unidentifiable tortfeasor doctrine will be misapplied in subsequent cases. Unidentifiable tortfeasor doctrines are fact specific and the danger of error is great. Courts can misapprehend key factual elements of a case, apply liability theories without recognizing the absence of essential elements and misunderstand the purpose of doctrinal components. Also, with respect to unidentifiable tortfeasor remedies relying on probability determinations, courts must remember that mathematical “proofs” are often replete with inadequacies, both in terms of mathematical error and nonsubstantiation of data.


Unidentifiable tortfeasor cases present difficult problems of uncertainty. Courts must deal not only with uncertainty about the commission of a tort but uncertainty concerning the identity of the tortfeasor. While the doctrine of res ipsa loquitur provides a means to deal with uncertainty, overcoming the tendencies exhibited in the Sargent line of cases, it does not, as a circumstantial evidence rule, address the unidentifiable tortfeasor situation.

From res ipsa loquitur and the separate notion of certain defendants having “superior access to information,” California courts developed the doctrine I have referred to as enhanced res ipsa loquitur. Enhanced res ipsa loquitur deals with uncertainty by shifting the burden of proof (and loss, if proof is not available) to defendants standing in a special relationship to plaintiffs or who can be characterized as responsible for the uncertainty. As evidenced by Ybarra, when these factors are present, enhanced res ipsa loquitur can be used with major impact in unidentifiable tortfeasor cases.

The concert of action theory and alternative liability theory are express unidentifiable tortfeasor doctrines. Although these doctrines appear in similar factual situations involving complementary action by two or more defendants, their theoretical underpinnings are quite different. Both are limited, however, in that the concert of action theory requires an agreement and the alternative liability theory requires a limited number of potential tortfeasors, all of whom are before the court.

The DES situation presents the unindentifiable tortfeasor problem dramatically. The California Supreme Court responded in Sindell by fashioning a new unindentifiable tortfeasor doctrine-market share liability. Although properly hailed as a breakthrough, market share liability was actually less of a departure from current norms than would have been stretching existing unidentifiable tortfeasor doctrines to apply to the DES situation.

Although important aspects of the doctrine are still unsettled, market share liability appears to be generally well-suited to the DES situation: A large amount of harm needs to be redressed, there is, at least at the pleading stage, the moral imperative presented by innocent plaintiffs and negligent defendants, the use of market shares and several liability makes for an effective remedy and evidence production worries are relatively mild. With the hypothetical blue bus case the reasons for providing a remedy are less compelling. There are significant concerns about evidence suppression, effectiveness and the magnitude of institutional burdens relative to the amount of harm to be redressed.

Although courts have erred and misapplied doctrines, California courts have generally done a good job handling unidentifiable tortfeasor situations. Their and other courts’ ability to continue to do so in the future will hinge upon their sensitivity to issues presented by unidentifiable tortfeasor situations and their creativity and flexibility in formulating well-tailored responses.

Stephen A. Spitz, 1990.

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