Recent Pennsylvania Court Rulings Weigh in on Expert Admissibility

Carolyn Casey, J.D.

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— Updated on December 7, 2020

Recent Pennsylvania Court Rulings Weigh in on Expert Admissibility

In Pennsylvania, three recent court decisions are revising the state’s rules governing expert testimony. The decisions discuss how the court may weigh in on expert methodology, if at all, and the line between lay and expert testimony. Attorneys practicing in the Keystone State will want to thoroughly review these decisions and learn how they may impact future use of expert witness testimony.

Challenges to Generally Accepted Methodology

Two of the new rulings cover the dos and don’ts for asking a court to rule that the opposition’s expert testimony is not based on generally accepted methodologies. One ruling admonishes judges for limiting their determinations in these challenges to the methodology only. The other case reminds would-be challengers of their burden to show that an expert methodology was novel before attempting to knock it out as an outlier.

Walsh v. BASF

In Walsh v. BASF, 234 A.3d 446, 2020 Pa., the Superior Court and the Supreme Court of Pennsylvania agreed that the trial judge erred in their decision on accepted expert methodology. The courts found that the lower court had gone beyond its scope of determining if the plaintiff’s expert used generally accepted methodologies to reach his conclusions on what level of benzene exposure could cause acute myeloid leukemia. The lower court rightly reviewed the methodologies that the expert employed— as outlined in supporting scientific articles—to assess the evidence on “general acceptance.” However, the Supreme Court held that the trial court erred when it determined that the relied upon methods did not support the expert’s conclusions. A concurring judge said, “Once the court determines, with the assistance of the proponent’s proofs and the accounts of fellow experts in the discipline, that the analysis proceeds from generally accepted principles and methods, the court may proceed no further.”

Commonwealth v. Bonnett

In Commonwealth v. Bonnett, 2020 Pa. Super. 231, defense counsel stumbled with a basic mistake in challenging expert testimony. The attorney claimed that the opposition’s fire causation expert’s methodology was outside of “the scientific methodology deemed acceptable in the fire investigative community.” However, they did not provide the court with evidence to support the challenge since they believed they did not have this burden of proof.

Here, the lower PA court denied a Frye hearing on the subject, upheld by the Superior Court. In failing to present expert testimony to show that the plaintiff’s expert had deviated from generally accepted methodologies, the defense was basically asking the court to evaluate the expert testimony and methodology without contrary proof—a request outside the role of the court.

Determining Lay vs. Expert Testimony in Jones

A third PA court decision examines the distinction between lay and expert testimony. In Commonwealth v. Jones, 2020 Pa. LEXIS 5622, at issue was whether a police detective’s layperson testimony about sexual abuse victim behaviors interfered with a jury’s role in deciding if the testimony is credible. After conviction and sentencing, the trial court denied the defendant’s post-sentencing motion that the detective’s testimony should not have been allowed.

On appeal, the defendant argued that the detective’s testimony constituted expert testimony based on specialized training and experience related to children and sexual assault. As such, the appellant asserted that the absence of the expert witness’s qualification meant the lower court should have precluded the testimony. The Superior Court upheld the trial court’s judgment that the witness was a lay witness and that the defense’s cross examination had remedied any damage that may have resulted.

The Appellate Court, however, wrestled with 42 Pa. C.S. Section 5920, which authorizes experts to testify on facts and opinions regarding types of victim responses and behaviors. The court also revisited a previous decision, Commonwealth v. Dunkle, 602 A.2d 830, which found that opinions concerning child sexual assault victim behavior are common layperson knowledge rather than special expertise. Moreover, the Dunkle court also held that expert testimony on the topic invades the jury’s role of determining witness credibility.

Upon reaching the Supreme Court, the case was sent the case back to the trial court to rule on admissibility considerations given the Dunkle decision and Section 5920. The Supreme Court ruled that Dunkle does not mean that all expert testimony on child sexual abuse must be banned due to interference with the jury’s role on credibility. This must be determined on a case by case basis. The high court also said this view is consistent with Section 5920’s mandate that experts may testify so long as they do not opine on the witness’s credibility.

The Dynamics of Expert Witness Testimony

Lawyers using expert witnesses in their cases must stay tuned into the dynamics of the law and new rulings in this sphere. Decisions and rulings are seldom static and require vigilance to learn and adopt new precedents. Armed with these nuanced insights, the savvy attorney will leverage expert witnesses most successfully.


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