Risk and Causation in the Law

In “Risk ≠ Causation,” I discussed the lack of scientific basis for confusing and conflating risk and cause.  For many years, the law was in accord, and plaintiffs could not substitute evidence of risk for evidence of cause in fact.  Some of the case law is collected, below.  The law in this area was fairly stable until Judge Weinstein’s important decision in the Agent Orange litigation, where the court confronted the limitations of epidemiologic evidence to support conclusions about specific causation. Judge Weinstein implicitly recognized the problem that very large relative risks certainly suggested that an individual case was likely to have been related to its antecedent risks.  Small relative risks suggested that any inference of specific causation from the antecedent risk was largely speculative, in the absence of some reliable marker of exposure-related causation. See In re Agent Orange Product Liab. Litig., 597 F. Supp. 740, 785, 817 (E.D.N.Y. 1984)(plaintiffs must prove at least a two-fold increase in rate of disease allegedly caused by the exposure), aff’d, 818 F.2d 145, 150-51 (2d Cir. 1987)(approving district court’s analysis), cert. denied sub nom. Pinkney v. Dow Chemical Co., 484 U.S. 1004  (1988); see also In re “Agent Orange” Prod. Liab. Litig., 611 F. Supp. 1223, 1240 (E.D.N.Y. 1985)(excluding plaintiffs’ expert witnesses), aff’d, 818 F.2d 187 (2d Cir. 1987), cert. denied, 487 U.S. 1234 (1988). 


Krim v. pcOrder.com, Inc., 402 F.3d 489 (5th Cir. 2005)(rejecting standing plaintiffs’ standing to sue for fraud absent a showing of actual tracing of sharings to the offending public offering; statistical likelihood of those shares having been among those purchased was insufficient to confer standing)

Howard v. Wal-Mart Stores, Inc., 160 F.3d 358, 359–60 (7th Cir. 1998) (Posner, C.J.)

Norman v. National Gypsum Co., 739 F. Supp. 1137, 1138 (E.D. Tenn. 1990)(statistical evidence of risk of lung cancer from asbestos and smoking was insufficient to show individual causation, without evidence of asbestos fibers in the plaintiff’s lung tissue)

Washington v. Armstrong World Industries, 839 F.2d 1121 (5th Cir. 1988)(affirming grant of summary judgment on grounds that statistical correlation between asbestos exposure and disease did not support specific causation)

Thompson v. Merrell Dow Pharm., 229 N.J. Super. 230, 244, 551 A.2d 177, 185 (1988)(epidemiology looks at increased incidences of diseases in populations) 

Johnston v. United States, 597 F.Supp. 374, 412, 425-26 (D.Kan. 1984)(although the probability of attribution increases with the relative risk, expert must still speculate in making an individual attribution; “a statistical method which shows a greater than 50% probability does not rise to the required level of proof; plaintiffs’ expert witnesses’ reports were “statistical sophistry,” not medical opinion)

Robinson v. United States, 533 F. Supp. 320, 330 (E.D. Mich. 1982)(finding for government in swine flu vaccine case; the court found that that the epidemiological evidence offered by the plaintiff was not probative, and that it “would reach the same result if the epidemiological data were entirely excluded since statistical evidence cannot establish cause and effect in an individual

Sulesky v. United States, 545 F. Supp. 426, 430 (S.D.W.Va. 1982)(swine flu vaccine GBS cases; epidemiological studies alone do not prove or disprove causation in an individual)

Olson v. Federal American Partners, 567 P.2d 710, 712 13 (Wyo. 1977)(affirming judgment for employer in compensation proceedings; cigarette smoking claimant failed to show that his lung cancer resulted from workplace exposure to radiation, despite alleged synergism between smoking and radiation).

Heckman v. Federal Press Co., 587 F.2d 612, 617 (3d Cir. 1977) (statistical data about a group do not establish facts about an individual).

Crawford v. Industrial Comm’n, 23 Ariz. App. 578, 582-83, 534 P.2d 1077, 1078, 1082-83 (1975)(affirming an employee’s award of no compensation because he was exposed to disease producing conditions both on and off the job; a physician’s testimony, expressed to a reasonable degree of medical certainty that the working conditions statistically increased the probability of developing a disease does not satisfy the reasonable certainty standard)

Guenther v. Armstrong Rubber Co., 406 F.2d 1315, 1318 (3d Cir. 1969)(holding that defendant cannot be found liable on the basis that it supplied 75-80% of the kind of tire purchased by the plaintiff; any verdict based on this evidence “would at best be a guess”). 

In re King, 352 Mass. 488, 491 92, 225 N.E.2d 900, 902 (1967)(physician expert’s opinion that expressed a mathematical likelihood that claimant’s death was caused by his accident was legally insufficient to support a judgment)

Garner v. Heckla Mining Co., 19 Utah 2d 367, 431 P.2d 794, 796 97 (1967)(affirming denial of compensation to family of a uranium miner who had smoked cigarettes and had died of lung cancer; statistical evidence of synergistically increased risk of lung cancer among uranium miners is insufficient to show causation of decedent’s lung cancer, especially considering his having smoked cigarettes)

Mahoney v. United States, 220 F. Supp. 823, 840 41 (E.D. Tenn. 1963)(Taylor, C.J.)(holding that plaintiffs had failed to prove that their cancers were caused by radiation exposures, on the basis of their statistical, epidemiological proofs), aff’d, 339 F.2d 605, (6th Cir. 1964)(per curiam)

Kamosky v Owens-Illinois Co., 89 F. Supp. 561, 561-62 (M.D.Pa. 1950)(directing verdict in favor of defendant; statistical likelihood that defendant manufactured the bottle that injured plaintiff was insufficient to satisfy plaintiff’s burden of proof)

Sargent v. Massachusetts Accident Co., 307 Mass. 246, 250 (1940)(“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 preponderance of the 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 preponderance 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 linger there.”)

Day v. Boston & Maine R.R., 96 Me. 207, 217–218, 52 A. 771, 774 (1902) (“Quantitative probability, however, is only the greater chance.  It is not proof, nor even probative evidence, of the proposition to be proved.  That in one throw of dice, there is a quantitative probability, or greater chance, that a less number of spots than sixes will fall uppermost is no evidence whatever that in a given throw such was the actual result.  Without something more, the actual result of the throw would still be utterly unknown.  The slightest real evidence would outweigh all the probability otherwise.”)


Federal Judicial Center, Reference Manual on Scientific Evidence 337 (2d ed. 2000)( “A final caveat is that employing the results of group-based studies of risk to make a causal determination for an individual plaintiff is beyond the limits of epidemiology. Nevertheless, a substantial body of legal precedent has developed that addresses the use of epidemiologic evidence to prove causation for an individual litigant through probabilistic means, and these cases are discussed later in this reference guide.”)

Special Committee on Science and Law, “An Analysis of Proposesd Changes in Substantive and Procedural Law in Response to Perceived Difficulties in Establishing Whether or Not Causation Exists in Mass Toxic Tort Litigation,” The Record of the Ass’n of the Bar of the City of N.Y. 905, 916, 920 (1986)(epidemiologic evidence cannot answer causation issue, with “any certainty,” in the case of an individual claimant whose disease occurs “naturally” in unexposed people).

Dore, A Proposed Standard for Evaluating the Use of Epidemiological Evidence in Toxic Tort and Other Personal Injury Cases, 28 Howard L.J. 677, 692 (1985)(individual causation questions are beyond the competence of epidemiologists and the description of epidemiology)

E. Cleary, et al., eds., McCormick on Evidence § 209, at 646 & n.1 (3d ed. 1984)( “In and of itself, statistical analysis can never prove that some factor A causes some outcome B.  It can show that in a sample of observations, occurrences of B tend to be associated with those of A, and it can suggest that this statistical association probably would be observed for repeated samples.  But the association, even though “statistically significant,” need not be causal.  For instance, a third factor C could be causing both A and B.  Thus, over some time period, there may be a correlation between the number of people smoking cigarettes and the number of certain crimes committed, but if told that the population was growing rapidly during this time, no one would think that this proves that smoking causes crime.  Experimental design and some forms of statistical analysis can help control for the effects of other variables, but even these merely help formulate, confirm or refute theories about causal relationships.”)

Cong. Research Serv. Library of Cong., Report to the Subcommittee on Science, Research and Technology, “Review of Risk Assessment Methodologies,” 95th Cong., 1st Sess. 11 (Mar. 1983)(recognizing that epidemiologic predictions of disease incidence among groups can establish establishing statistical associations, but show specific causation) 

Solomons, “Workers’ Compensation for Occupational Disease Victims:  Federal Standards and Threshold Problems,” 41 Alb. L. Rev. 195, 201 (1977)(“suggesting that epidemiological showing a high probability of employment relatedness of lung cancer in an asbestos insulation worker, for example, would probably not establish causation in an individual claim.”) 

Estep, “Radiation Injuries and Statistics:  The Need for a New Approach to Injury Litigation,” 59 Mich. L. Rev. 259, 268-69 (1960)

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