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Dechert LLP
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Reasonable Certainty and Defense Experts
Thursday, August 04, 2011
The other day we saw the Nevada Supreme Court’s decision in Williams v. Eight Judicial
District Court, ___ P.3d ___, 2011 WL 3206963 (Nev. July 28, 2011). One of the two “novel”
questions the court decided in Williams is “whether defense expert testimony offering
alternative causation theories must meet the ‘reasonable degree of medical probability’
standard” as plaintiff-side experts. Id. at *1. The Nevada court unanimously held that,
because defendants don’t have the burden of proof, defense experts’ opinions don’t have to
meet that standard, because that would effectively be shifting the burden of proof to the
defendant:
“[W]hen a defense expert's testimony is used to contradict a plaintiff's causation theory by comparing that
theory to other plausible causes, each additional cause does not need to be stated to a greater-than-50-
percent probability. To hold otherwise would severely hinder a defendant’s ability to undermine the
causation element of the plaintiff's case and could result in an unfair shifting of the burden of proof to the
defendant.”
2011 WL 3206963, at *7. The court relied primarily on Wilder v. Eberhart, 977 F.2d 673 (1st
Cir. 1992), which reached a similar result under New Hampshire law:
“Were we to accept plaintiff’s argument that once a plaintiff puts on a prima facie case, a defendant cannot
rebut it without proving another cause, the resulting inequities would abound. For example if ninety-nine out
of one hundred medical experts agreed that there were four equally possible causes of a certain injury, A, B,
C and D, and plaintiff produces the one expert who conclusively states that A was the certain cause of his
injury, defendant would be precluded from presenting the testimony of any of the other ninety-nine experts,
unless they would testify conclusively that B, C, or D was the cause of injury. . . . We think that such a result
does not reflect the state of the law in New Hampshire, and furthermore would be manifestly unjust and
unduly burdensome on defendants.”
Id. at 676-77.
We nodded when we saw that, because we’re quite familiar with this rationale from cases
decided under Pennsylvania law. In Pennsylvania, a defense expert need not (although we’d
certainly prefer that they did) offer any opinions to a reasonable degree of medical certainty,
