The new science of eyewitness memory

The prevailing view among criminal justice and legal practitioners, and the general public, is that eyewitness evidence is generally inaccurate and unreliable. Here we argue that that perspective fails to take the full cognitive context of eyewitness reports into account. A broader view of eyewitness cognition includes both memory judgments—for example, the selection of an individual from a lineup—and an accompanying metacognitive context—for example, the level of confidence that an eyewitness places in that selection. When these components are considered jointly, eyewitness evidence is highly reliable and can be treated like any other source of evidence in the courtroom—valuable when appropriately assayed but prone to contamination. Empirical research over the past 10 years, based on the bedrock principles of Signal Detection Theory, has illuminated problems with standard historical measures that are based on intuitive theorizing about measurement. Those measures, and the results from experiments that utilize them, have misled the field regarding reform efforts and have diminished the role that eyewitness confidence should play in distinguishing accurate from inaccurate identifications. Signal detection theory, coupled with ROC analysis and confidence calibration, is pointing toward a new science of eyewitness memory. The new science shifts the blame for faulty testimony from unreliable eyewitnesses to other actors in the law enforcement and legal community—actors whose behaviors can transform low-confidence, likely inaccurate, initial identifications, into incorrect, high-confidence, courtroom identifications. Signal detection theory also highlights the role that other metacognitive factors play, as well as how to balance the two types of errors—false identifications of the innocent and missed identifications of the guilty—that inevitably arise from the eyewitness decision problem. The new science of eyewitness memory is leading a transformation in how eyewitness evidence can and should be used by the criminal justice system.