Pennsylvania Supreme Court issued a decision which overturns its previous ban on expert testimony regarding eyewitness identification.  

For years, social scientists have conducted studies on the unreliability of eyewitness accounts following crimes.  Prior to this decision, however, Pennsylvania law prevented juries from hearing this testimony. Now, this decision allows the defense to call an expert witness to testify about the issues of unreliability in the accounts of eyewitnesses due to the high levels of stress the eyewitnesses endure during the commission of a crime.

The Supreme Court’s decision essentially allows the trial court to determine in what cases the expert testimony would be relevant and the extent of which the expert could testify.  Generally, the expert’s testimony must be limited to general studies and findings of unreliability and may not comment on a specific eyewitness in a case.