Interesting Rule 702 Causation Case

In Tamraz v. Lincoln Electric Co., the Sixth Circuit recently overturned a district court verdict awarding $20 million to a plaintiff who claimed that his manganese exposure in the workplace led to his Parkinson’s disease. Judge Jeffrey Sutton wrote an excellent opinion for the majority. Judge Boyce Martin dissented.

Judge Sutton and Judge Martin both seem to agree that the the connection between the exposure and Parkinson’s is, as Judge Martin put it, “the subject of valid scientific debate and publication.” Judge Martin, however, argued that the plaintiff’s expert may rely on his “general experience and knowledge, and theoretical medical writing that explored the connection between manganese exposure and Parkinson’s Disease.” Judge Sutton, by contrast, demanded that the expert actually present reliable, non-speculative “scientific knowledge.”

The difference, ultimately, is that Judge Sutton relied on the language of Federal Rule of Evidence 702, which governs the admissibility of expert testimony, and Judge Martin did not.

Here’s Judge Sutton on the plaintiff’s expert’s hypothesis:

That is a plausible hypothesis. It may even be right. But it is no more than a hypothesis, and it thus is not “knowledge,” nor is it “based upon sufficient facts or data” or the “product of reliable principles and methods . . . applied . . . reliably to the facts of the case.” Fed. R. Evid. 702.

By contrast, Judge Martin, though able to find supporting language from various precedents and law review articles, never grapples with the rather stark and clear text of Rule 702. Indeed, his dissent doesn’t cite, quote, or discuss the language of Rule 702 at all.

So it’s worth reiterating a point I’ve made before. Rule 702, promulgated in 2000, and not the more ambiguous Daubert or Kumho Tire opinions, decided in 1993 and 1999 respectively, is what dictates the scope of admissible expert testimony. Any interpretation of Daubert, Kumho Tire, or the 1997 Joiner case that conflicts with the subsequent statute, Rule 702, is legally incorrect.