Conning the IADC newsletters.

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Recognizing that a wide range of practical and helpful material appears in the newsletters prepared by committees of the International Association of Defense Counsel, this department highlights interesting topics covered in recent newsletters and presents excerpts from them.

Common Pitfalls of General Causation Proof

Writing in the May 2004 newsletter of the Toxic and Hazardous Substances Litigation Committee, D. Ferguson McNiel III and Alan B. Daughtry of the Houston office of Vinson & Elkins discuss proof in toxic tort and drug cases:

Two causation principles apply in tort cases. General causation concerns whether a substance is capable of causing a particular injury or condition in the general population, while specific causation determines whether a substance actually caused a specific individual's injury or condition. Reference Manual on Scientific Evidence 444 (Federal Judicial Center, 2d ed. 2000); Merrell Dow Pharmaceuticals Inc. v. Havner, 953 S.W.2d 706, 714 (Tex. 1997). In most toxic tort and drug cases, direct scientific experimentation cannot be used to determine specific whether a substance potentially causes an injury or condition. Plaintiffs therefore will attempt to establish general causation circumstantially by showing that the incidence of disease or injury is sufficiently elevated owing to exposure to a substance. See generally

Daubert v. Merrell Dow Pharmaceuticals Inc., 43 F.3d 1311, 1320 n.13 (9th Cir. 1995) (on remand).

General causation

Plaintiffs cannot avoid the general causation requirement. The substance must be capable of causing the plaintiff's injury or condition. Many plaintiffs have attempted to bypass the need for this indirect general causation proof by relying on a differential diagnosis--a clinical process whereby a doctor determines what caused a plaintiff's symptoms by ruling out alternative possible causes. This happened in Heller v. Shaw Industries Inc., 167 F.3d 146, 156 (3rd Cir. 1999), and In re Paoli Railroad Yard PCB Litigation, 35 F.3d 717, 755, 758 (3rd Cir. 1994).

Some courts have held that a differential diagnosis--typically coupled with a strong temporal association between exposure and onset of symptoms--may supplant the need for general causation proof that a substance is capable of causing an injury or condition. See, e.g., Turner v. Iowa Fire Equipment Co., 229 F.3d 1202, 1208-09 (8th Cir. 2000); Heller, 167 F.3d at 154-55; and Zuchowicz v. United States, 140 F.3d 381, 385, 389-90 (2d Cir. 1998). But this approach puts the cart before the horse. One must be able to "rule in" a putative cause before reaching a causal conclusion by ruling out other causes. See Michael B. Kent Jr., Daubert, Doctors and Differential Diagnosis: Treating Medical Causation Testimony as Evidence, 66 DEF. COUNS. J. 525, 532 n.2 (1999).

The trend in drug and toxic tort cases is to require general causation proof: a differential diagnosis is indicative of only specific causation. See, e.g., Goebel v. Denver & Rio Grande Western Railroad Co., 346 F.3d 987, 998 (10th Cir. 2003) (reliable differential diagnosis admissible given "valid showing of general causation"); Hollander v. Sandoz Pharmaceuticals Corp., 289 F.3d 1193, 1211 (10th Cir. 2002); Glastetter v. Novartis Pharmaceuticals Corp., 252 F.3d 986, 989 (8th Cir. 2001); Meister v. Medical Engineering Corp., 267 F.3d 1129, 1131 (D.C. Cir. 2001); Black v. Food Lion Inc., 171 F.3d 308, 312-14 (5th Cir. 1999); Cavallo v. Star Enterprises, 892 F.Supp. 756, 771-72 (E.D. Va. 1995), aff'd on same grounds, rev'd on other grounds, 100 F.3d 1150, 1159 (4th Cir.); Coastal Tankships U.S.A. Inc. v. Anderson, 87 S.W.3d 591, 608-09 (Tex. App.--Houston [14th Dist.] 2002, pet. denied). See also Joseph Sanders & Julie Machal-Fulks, The Admissibility of Differential Diagnosis Testimony to Prove Causation in Toxic Tort Cases: The Interplay of Adjective and Substantive Law, 64 LAW & CONTEMP. PROBLEMS 107, 122-24 (2001) (compiling cases), and Harvey Brown, Eight Gates for Expert Witnesses, 36 Hous. L. REV. 743, 849 (Fall 1999) (compiling cases).

Pitfalls for plaintiffs

General causation poses many pitfalls for plaintiffs. Given this recent trend of courts' refusing to allow general causation to be supplanted by the specific causation proof of a differential diagnosis, it is useful to highlight some of the many pitfalls in general causation proof. Most recent cases focus on specific causation, but general causation affords defendants ample opportunities for attacking a plaintiff's causation proof. Because epidemiological studies--the most widely accepted form of general causation proof--is expensive and time consuming to develop, plaintiffs often are tempted (or forced) to rely on general causation evidence that is not appropriately tailored to their cases.

Here are a few basic examples of shortfalls in general causation proof.

Agency finding

An agency finding that a substance is harmful is typically not enough for general causation. Many plaintiffs assume that a public health agency's finding that a substance is hazardous is sufficient to establish a basis for causation. To the contrary, there is abundant authority holding that such materials are not legally sufficient evidence of causation. Moore v. Ashland Chemical Co., 151 F.3d 269, 278 (5th Cir. 1998); Allen v. Pennsylvania Engineering Corp., 102 F.3d 194, 198 (5th Cir. 1996); Coastal Tankships, 87 S.W.3d at 611.

This result typically is explained by the differing standards governing the agency's decision, as noted by the Fifth Circuit in Allen:

Regulatory and advisory bodies such as IARC, OSHA and EPA utilize a "weight of the evidence" method to assess the carcinogenicity of various substances in human beings and suggest or make prophylactic rules governing human exposure. This methodology results from the preventive perspective that the agencies adopt in order to reduce public exposure to harmful substances. The agencies' threshold of proof is reasonably lower than that appropriate in tort law. [102 F.3d at 198] The federal district court for the Middle District of North Carolina reached the same result in Dunn v. Sandoz Pharmaceuticals Corp., 275 F.Supp.2d 672 (M.D. N.C. 2003), in which the plaintiffs tried to rely on a Food and Drug Administration determination that the drug Parlodel "might cause seizures or strokes in women already susceptible to disease." The court held that the FDA's determination was not sufficient evidence of causation, explaining that the balancing of risks employed by the agency was different from the threshold standard for establishing causation in tort cases:

The FDA decided that "the potential risks associated with the use of bromocriptine is no longer shown to be safe for use in preventing physiological lactation." 59 Fed. Reg. at 43351. The FDA is concerned with safety and risk benefit analysis: if the risks outweigh the benefits, the FDA may take regulatory action. The FDA balanced Parlodel's possible harm against its limited beneficial use. The...