The Pennsylvania Supreme Court’s decision succinctly begins:

In this appeal by allowance we address the question of whether a trial court may, in its discretion, permit expert testimony in the area of eyewitness identification, and, in doing so, we reconsider our current decisional law which absolutely bans such expert testimony. For the reasons that follow, we hold that, in Pennsylvania, the admission of expert testimony regarding eyewitness identification is no longer per se impermissible, and join the vast majority of jurisdictions which leave the admissibility of such expert testimony to the discretion of the trial court. Thus, we reverse the order of the Superior Court, and remand the matter to the trial court for reconsideration of such expert testimony, including the possibility of a Frye hearing in light of our decision today.

— Commonwealth of Pennsyvania v. Benjamin Walker, 92 A.3d 766 (Pa. 2014)

The full opinion may be found here (log-in required).