Wyeth v. Rowatt: Substantial Confusion About Causation
Reading and re-reading and even re-re-re-reading the Nevada Supreme Court's opinion in Wyeth v. Rowatt only leaves me more perplexed about Nevada's take on causation in pharma/toxic tort cases. Typically a plaintiff must prove that if she hadn't been exposed to defendant's product she'd have been better off. In other words, defendant's product was a "but for" cause of her injury. There are of course cases that relieve plaintiff of having to prove to which of several defendants' identical products she was exposed (e.g. Sindell v. Abbott Laboratories) but she always has to prove, irrespective of who made it, that the product complained of is actually what made her ill.
The court in Wyeth v. Rowatt held that the following jury instruction was either OK or at least not harmful: "A legal cause of injury, damage, loss, or harm is a cause which is a substantial factor in producing or promoting the injury, damage, loss, or harm." Nevada has an instruction on "but for" causation and plaintiffs and defendant all requested it. However, the trial court instead gave a modified pattern jury instruction for substantial factor causation that reflected its understanding of the promoter theory of carcinogenesis - the idea that some things initiate cancer and other things propel or promote it, with hormone replacement therapy allegedly falling into the latter category - and stuck it not into the pattern instruction for "but for" causation but rather into the instruction on substantial factor causation. The pattern substantial factor causation instruction is to be used when the jury is confronted with two competing causes, either of which "would have been sufficient to cause the injury".
How can a promoter be a sufficient cause? It can't of course, but that's just a quibble about loose language. The real problem is that any sufficient cause, absent a superseding cause, is necessarily the "but for" cause and "substantial factor causation" is just "but for" causation + reasonableness so why not require the "but for" instruction in either instance unless you're watering down the causation standard?
In Texas we had an instruction similar to that used by the trial court in Rowatt. It was the old instruction for a "Producing cause" and years of jury trials and focus group experience conclusively demonstrated that the instruction - "Producing cause' means an efficient, exciting, or contributing cause that, in a natural sequence, produces the incident in question. There may be more than one producing cause" - led jurors to believe that they were permitted to find causation whenever the putative cause might have or could have been one among a constellation of possible causes. The Texas Supreme Court finally made the instruction conform to the law in 2007 with it's opinion in Ford Motor Company v. Ledesma writing that the components of a producing cause are "that (1) the cause must be a substantial cause of the event in issue and (2) it must be a but-for cause, namely one without which the event would not have occurred."
Within the Rowatt opinion is a brief discussion of risk but rather than using it to inform the state's "substantial factor causation" jurisprudence the court instead held that a four-fold increase in risk claimed by plaintiff's expert somehow made the lack of the "but for" instruction harmless. So are they saying that anytime relative risk is above two, causation is established? They don't say anything like that and even if they did it still has to be (everywhere else) a "but for" cause. The big risk increase is just a way to satisfy the preponderance of the evidence burden on "but for" causation.
If you've got an insight into how Rowatt fits within a modern conception of causality in the law I'd appreciate it if you'd drop me an email re: same.