On May 28, 2014, the Pennsylvania Supreme Court held that trial courts may now allow expert testimony on the question of eyewitness identification if the judge believes, under the totality of the circumstances of a particular case, it is appropriate and would assist the jury to make an informed decision.
In Commonwealth v. Walker, the defendant was charged with several offenses arising out of two armed robberies committed on separate dates against different victims. The only evidence linking the defendant to the crimes were the pre-trial and in court identifications of him as the assailant by the victims. The trial court denied the defendant’s request to present expert testimony regarding the reliability of eyewitness identifications. The defendant was acquitted of the first robbery, but convicted on several charges related to the second. On appeal, the Superior Court affirmed the trial court’s denial of the admission of expert testimony regarding eyewitness identification. That evidence had long been held by our courts as inadmissible per se.
On review, the Supreme Court held that a trial court should have the discretion to permit the testimony of an expert in the field of eyewitness testimony. The Court’s rationale for lifting its former absolute ban on such testimony was based on a review of the law in other jurisdictions along with the numerous studies regarding issues that may affect the reliability of eyewitness identification. Many state and federal courts have permitted the testimony after finding it to be generally accepted within the scientific community. The Court further found that allowing such testimony, in limited circumstances, would not invade the province of the jury in making decisions regarding credibility. Rather, such testimony would educate the jury about factors that could impact eyewitness identification and allow them to make a more informed decision.
In reaching its decision, the Court made clear that the ruling is limited to expert testimony regarding eyewitness identification and does not change the law as to general principles regarding expert testimony. It also does not make expert testimony regarding eyewitness identification admissible per se. It simply permits the trial court to weigh all factors in a particular case and determine if such testimony would be appropriate. As a prerequisite to admission, a defendant will be required to make an on their accord, detailed proffer to the court, with an explanation of precisely how the expert’s testimony is relevant to the eyewitness identifications under consideration and how it will assist the jury in its evaluation. The Court made no ruling as to the admissibility of the proffered testimony in Walker’s case, but rather remanded the matter to the trial court for a hearing in order to determine if its admission was appropriate.