Approaches to The Exclusion of Expert Witness Testimony

In Daubert v. Merrell Dow Pharmaceuticals, Inc., the petitioners, the parents of two minor children, sought to sue Merrell Dow on the grounds that their use of a prescription anti-nausea medication, Bendectin, during pregnancy, caused their children’s birth defects. The suit was originally dismissed after the District Court reviewed an affidavit from a “well credentialed expert.” This expert wrote the literature did not support the petitioners’ position that Bendictin leads to birth defects in humans despite the petitioners presenting the following evidence:

• Testimony of eight of their own “well credentialed experts” who opined Bendictin caused birth defects in animals
• Chemical structure analyses of the drug
• An unpublished reanalysis of previously published human statistical studies

The District Court made their ruling holding the petitioner’s evidence did not meet the general acceptance standard as outlined in Frye v. United States, 293 F.1013 (1923).

The Supreme Court reversed the District Court, holding the Federal Rules of Evidence, in particular, Federal Rule of Evidence 702 properly imposed the limits of admissibility of scientific evidence. Commonly referred to as “the Daubert factors,” the court found the following factors should be considered by the court when assessing the admissibility of expert testimony:

1. Whether the theory or technique in question can be (and has been) tested
2. Whether it has been subjected to peer review and publication
3. Its known or potential error rate
4. The existence and maintenance of standards controlling its operation, and
5. Whether it has attracted widespread acceptance within a relevant scientific community

The court also noted the judge should be mindful of other applicable rules regarding admissibility. Id. 592 – 595.

The trial court has broad discretion in determining the admissibility of experts, in whole or in part. There is at least some indication federal courts are far more likely to admit experts the prosecution offers in criminal cases than the experts offered by criminally charged defendants. Further, it appears the appellate federal courts are far more likely to question the trial court’s judgment of the admissibility of purported scientific evidence in civil cases over criminal cases.

In granting motions challenging expert testimony, courts have taken three approaches, depending on the circumstances.

Exclusion Based on Daubert Factors

When an expert’s testimony is excluded, the court may rely on the failure of the attorney offering the expert to establish the Daubert factors have been met. This may be due to the failings of the attorney, or the court’s belief a science has not advanced to the stage of meeting the Daubert factors. A scientific method in its infancy may be too new to have been subject to rigorous peer review and publication. Because the Daubert factors allow a court to use their judgment, a court may find a lack of an error rate to be perfectly acceptable, and permit the testimony, or may find the lack of an established error rate an indication the field has not been studied enough to be sufficiently reliable.

Limitations Based on Daubert Factors

Courts may limit the admissibility of certain expert testimony based on facts and circumstances. For example, in United States v. Willock, a Magistrate limited a firearms examiner’s testimony to opinions and the bases for the opinions “without any characterization as to degree of certainty.” It was determined the examiner found no meaningful distinction after testifying his identification with “an absolute certainty” stating, “the likelihood of another firearm having fired these cartridges is so remote as to be considered a practical impossibility.” United States v. Willock, 696 F. Supp. 2d 536, 572–73 (D. Md. 2010).

But it is not just the courts who are issuing limitations. In September of 2016, then Attorney General Loretta Lynch issued a Memorandum for Heads of Department Components directing all federal forensic laboratories to review their policies and procedures, ensuring their forensic scientists were no longer testifying to a “reasonable scientific certainty” or to a “reasonable [forensic discipline] certainty” in reports or in testimony. Further, Department prosecutors were instructed to abstain from using these expressions when either presenting forensic reports or when questioning forensic experts in court, except where required by law or by a presiding judge.

Exclusion Based on Other Rules of Evidence

Of course, the Daubert factors aren’t the only basis to exclude expert testimony. In order to be admissible, a party must establish an expert as one “qualified as an expert by knowledge, skill, experience, training, or education.” Federal Rule of Evidence 702. There are three situations where this may present itself. The first is when a party seeks to offer testimony from one not qualified on any front regarding a topic at issue. The second is when the witness is not helpful to the trier of fact, regardless of their qualifications. Finally, when a party seeks to introduce testimony beyond the bounds of their qualifications, the court may exclude their testimony.

An Expert Not Qualified

In some instances, a court will prevent an offered expert witness from testifying at all. The court may decide the expert does not have sufficient knowledge to assist the trier of fact in understanding the evidence. This is a judgment call. The party introducing the testimony bears the burden of establishing qualifications. As such, attorneys should be mindful of their responsibility. Experts can assist by providing information to lay the proper foundation.

An Expert Not Helpful

Alternatively, the court may find the expert can’t assist the trier of fact in determining a particular fact at issue in a case. For example, imagine an expert offered to testify a particular individual is “predisposed” to undue influence. Will this help a jury decide whether the person was unduly influenced in a given case? If not, even if the expert is fully qualified to testify about predisposition, the court may reject the expert’s testimony.

An Expert Testifying Beyond the Bounds of Their Expertise

An expert in arson, for example, probably is not in a position to opine about whether the autopsy photos indicate the presence of smoke in the lungs of a person found dead at the scene of a fire. An expert in cancer-causing chemicals may not have the requisite “knowledge, skill, experience, training, or education” to testify about the effects of antidepressants combined with excessive alcohol use.

It is not uncommon, with a scientist on the stand, for attorneys to ask for information about things beyond the expertise of the testifying expert. In this particular situation, both the expert and the attorneys have a certain amount of responsibility. Attorneys should object if an expert is asked for information beyond their expertise. However, experts should also refrain from offering speculation or otherwise testifying beyond their training and experience.

Courts as Gatekeepers

At the end of the day, judges are charged with being gatekeepers of evidence. However, attorneys and experts themselves also have a duty to exercise care when soliciting or providing testimony.