“Do Not Tell Fish Stories Where The People Know You; But Particularly, Don’t Tell Them Where They Know The Fish.”

Thus sayeth the 11^th Circuit, quoting Mark Twain in a recent, unpublished opinion, and ruling that a district court had not abused its discretion in allowing an expert to testify regarding causation.  The case, Southern States Cooperative, Inc. v. Melick Aquafeeds, Inc., 2012 U.S. App. LEXIS 7653 (11^th Cir., Apr. 17, 2012), involved a dispute between a commercial producer of tilapia and the company supplying it feed.  The district court allowed expert testimony from a “doctor of fish nutrition” on behalf of the plaintiff, and over the defendant’s Daubert objections.  The 11^th Circuit, after quoting Mark Twain, stated “in this case, we know the fish – and the facts . . .”  Id. at *5.

The significance of the opinion is the 11^th Circuit’s discussion of the expert’s differential etiology testimony.  The Court noted that “Differential etiology is a process of elimination in which (1) an expert compiles all possible causes of an injury, and (2) he rules out each of the potential causes ‘until reaching one that cannot be ruled out or determining which of those that cannot be excluded is the most likely.’”  Id. (citations within omitted).  The defendant challenged the expert based on the failure to complete step 2, claiming the expert did not scientifically rule out alternative causes but instead “assumed them away.”  The 11^th Circuit reiterated that when ruling out causes in the second step, an expert “must provide reasons for rejecting alternative hypotheses using scientific methods and procedures and the elimination of those hypotheses must be founded on more than subjective beliefs or unsupported speculation.”  Id. at *6-7.

However, in what appears to be a subtle change to the standard of review for “differential etiology” expert testimony (which the 11^th Circuit said is interchangeable with “differential diagnosis”), the 11^th Circuit ruled where a challenge to an expert is based on the expert not providing persuasive or sufficient explanation for ruling out causes, this is not a basis to exclude such testimony.  The Court noted that its “role as a gatekeeper ‘is not intended to supplant the adversary system or the role of the jury:  [v]igorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence.’”  Id. at *8 quoting Allison v. McGhan Medical Corp., 184 F.3d 1300, 1311 (11^th Cir. 1999)(citations omitted).  The Court concluded that the defendant’s contentions spoke to the weight to be afforded the expert’s testimony, not its admissibility, and thus not within the Court’s province to evaluate.  This suggests the 11^th Circuit is taking a more deferential approach to expert testimony based on “differential diagnosis,” making it likely that more “fish stories” may survive and be presented to juries in the future.