If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.37

The commentary accompanying the revised rule38 recites the “Daubert factors” and then goes on to explain that:

Courts both before and after Daubert have found other factors relevant in determining whether expert testimony is sufficiently reliable to be considered by the trier of fact. These factors include:

  1. Whether experts are proposing to testify about matters growing naturally and directly out of research they have conducted independent of the litigation, or whether they have developed their opinions expressly for purposes of testifying.

  2. Whether the expert has unjustifiably extrapolated from an accepted premise to an unfounded conclusion.39

  3. Whether the expert has adequately accounted for obvious alternative explanations.

  4. Whether the expert is being as careful as he would be in his regular professional work outside his paid litigation consulting.

  5. Whether the field of expertise claimed by the expert is known to reach reliable results for the type of opinion the expert would give.40

All of these factors remain relevant to the determination of the reliability of expert testimony under the rule as amended.

The commentary accompanying the revised rule also notes that:


FED. R. EVID. 702.


FED. R. EVID. 702 advisory committee’s note (2000 Amendments) (citations and quotation marks omitted).


The commentary cites General Electric, 522 U.S. at 146 (noting that in some cases a trial court “may conclude that there is simply too great an analytical gap between the data and the opinion proffered”).


The commentary cites Kumho Tire, 526 U.S. at 150 (Daubert’s general acceptance factor does not “help show that an expert’s testimony is reliable where the discipline itself lacks reliability, as for example, do theories grounded in any so-called generally accepted principles of astrology or necromancy.”); Moore v. Ashland Chem., Inc., 151 F.3d 269 (5th Cir. 1998) (en banc) (clinical doctor was properly precluded from testifying to the toxicological cause of the plaintiff ’s respiratory problem, where the opinion was not sufficiently grounded in scientific methodology); Sterling v. Velsicol Chem. Corp., 855 F.2d 1188 (6th Cir. 1988) (rejecting testimony based on “clinical ecology” as unfounded and unreliable).

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement