The identification of College junior Bryan Warner as the gunman in the Jan. 26 shooting of a West Philadelphia man may be flawed, some experts say.
The victim and an independent witness both picked Warner out of a photo lineup following the incident, resulting in Warner's arrest, Philadelphia Police Lt. John Walker said.
The two eyewitness accounts are the main sources of evidence linking Warner to the shooting.
But according to Iowa State psychology professor Gary Wells -- who helped write a Justice Department guide on this type of identification -- eyewitness testimony can be one of the more unreliable pieces of evidence, especially in high-stress incidents.
"Generally, what happens when events like this occur [and] there's a weapon or gunshot involved, there's stress," Wells said. Eyewitnesses "may think that they remember the details, but they actually recorded relatively little information."
Wells added that providing the photos in a sequential order rather than all at once increases accuracy.
"If you give the photos sequentially, the advantage is that you can't just compare one person to another and say who looks most like" the culprit, Wells said.
Walker said the victim named Warner as the culprit after he was presented with a layout of eight photos at the same time.
Wells added that police should explicitly mention that the culprit may not be included in the lineup.
Philadelphia Police detective Matt Farley said that police abide by this procedure.
Wells added that even confident eyewitnesses are often wrong in their lineup selections.
"If the witness picks this person [and] the detective who is administering it gives some kind of feedback that 'That's the [suspect],' the witness becomes more positive that they were right," he said.
While Penn Law professor Claire Finkelstein agreed that eyewitness accounts are often unreliable, she argued that a second identification by an independent witness -- as in Warner's case -- can considerably improve the prosecution's case.
"It substantially strengthens the testimony of each eyewitness when [that testimony] is corroborated by a second eyewitness," she said.
But Wells noted that even multiple eyewitness identifications can be false, recalling a man who was wrongly imprisoned in 1984 after the testimony of five separate eyewitnesses identified him.
"People are impressed when two [witnesses] pick the same person from a photo lineup, but the fact is that if an eyewitness is going to make an error ... another eyewitness is prone to make the same error," he said.
Warner's lawyer, Richard Harris, suggested that the victim and the eyewitness could have both intentionally misidentified Warner out of fear of their own safety.
"The reality was that [Warner] wasn't there," Harris said. "If there were two people or 20 people [identifying him], they were wrong."
And Walker said that police prefer not to rely on eyewitness testimony.
"It's always good to get eyewitness testimony corroborated with physical evidence in the scene, but sometimes that's just not possible," he said.
Harris said he would consider the possibility of arguing for a lineup of actual people from which the victim is asked to identify the shooter at a preliminary hearing on Thursday. Still, he said he believed such a lineup would probably be tainted considering the publicity that Warner's case has received.
