If you've followed the criminal law or watched much TV, you're probably aware of "the lineup." An eyewitness to a crime stands behind smoked glass and chooses the perpetrator from a line of five or six people. It can also be done using photographs -- the witness pages through an array of photographs until he or she recognizes the perp.
The trouble is, it's just too easy for law enforcement to skew the outcome, whether they mean to or not.
You can easily imagine any number of scenarios where that could happen. The victim's description, for example, might have said the perp was a white guy with a mustache. The officer finds there aren't enough comparison photos available of white men with mustaches and uses what he can find -- but the resulting photo array contains only one subject that looks like the description.
Criminal defense attorneys and prosecutors alike are well aware of the problem, and it appears the Justice Department is, as well. To help prevent biased or unrepresentative photo arrays, the agency has just released new guidelines for federal law enforcement on how to conduct them properly.
Photo arrays should always be presented blind and the witness's level of surety recorded
Justice recommends that police use "blind" and/or "blinded" procedures when preparing a photo array for an eyewitness. In a "blind" procedure, the investigating agent is not given the witness's description or other information about the suspect's appearance. In a "blinded" process, the agent may know the suspect's appearance but is prevented from seeing the order the photos are presented in. This is meant to prevent the agent from signaling a desired result, either intentionally or unintentionally.
In addition, during trial it can be extremely important to know how confident the eyewitness was in their identification. Justice advises agents to ask the witness directly about his or her level of certainty and then document the answer, either by taping the witness's reaction or transcribing what the witness said.
According to a legal expert interviewed by NPR, these recommendations aren't surprising. They represent best practices developed using scientific research.
The guidance legally applies only to federal law enforcement agencies and to give federal prosecutors additional information when deciding how much weight to give a witness's identification. However, state law enforcement often follows advice promulgated by the Department of Justice.