The Supreme Court this week made it harder for criminal defendants to challenge one of the most common flaws in the criminal justice system: the use of mistaken eyewitness evidence. The 8-1 decision needlessly narrows the ability of judges to suppress eyewitness testimony marred by inconsistency or other indications of error, leaving the task of evaluating the reliability of such evidence to juries.
Statistics show that 76% of 250 convictions overturned since 1989 because of DNA evidence involved mistaken eyewitness identification. A host of factors can lead to mistakes. Most are attributable to manipulation by the police, such as lineups or photo arrays in which the suspect is grouped with people who look nothing like him. There is also evidence that a witness has a harder time making a correct identification when he and the suspect are of different races.
Courts, legislatures and police departments admirably have taken steps to prevent officers from unduly influencing witnesses. For example, 21 police departments in California conduct "blind" photo lineups, in which the person administering the viewing doesn't know who the suspect is. Perhaps most important, the Supreme Court has ruled that judges may suppress eyewitness testimony before trial if there is evidence that police "have arranged suggestive circumstances leading the witness to identify a particular person as the perpetrator of a crime." This is an important safeguard because jurors tend to give too much weight to eyewitness testimony, even if the judge advises them that it can be fallible for various reasons.