Legal Memorandum: Testimony by Expert Witnesses

Issue: Under the federal rules, does an expert opinion require support beyond the ipse dixit of the expert?

Expert opinions based solely on speculation and without support should be excluded:

The trial court’s gatekeeping function requires more than simply “taking the expert’s word for it.” “[N]othing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert.” 

General Elec. Co. v. Joiner, 522 U.S. 136, 146 (1997) (citations omitted), quoted in U.S. v. Nacchio 555 F.3d 1234, 1258 (10th Cir. 2009).  See also Fed. R. Evid. 702(b) (testimony may not be admitted unless "based on sufficient facts or data"). 

“[W]hen the conclusion simply does not follow from the data, a district court is free to determine that an impermissible analytical gap exists between premises and conclusion.”  Norris v. Baxter Healthcare Corp., 397 F.3d 878, 886 (10th Cir. 2005).  “[W]here expert ‘offers no data, no source of information and no . . . evidence to back up his bald assertions[,] [t]his is precisely the kind of ipse dixit of the expert that does not meet the standards of Rule 702 or Daubert.‘” Gallegos v. Swift & Co. 237 F.R.D. 633, 640 (D. Colo. 2006).

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