Extract

, usually conducted by police and prosecutors. Later chapters will address in more detail forensic techniques normally conducted by laboratory technicians (see §§8.4.3; 11.4.3).

Eyewitness-driven identifications are the leading cause of wrongful convictions.1 Years of research explain why.2 Perception of a crime can be obscured not only by poor eyesight or bad lighting, but by the stress associated with the crime, a focus on weapons rather than faces, short observation time, and “seeing” what the witness expected or wanted to occur rather than what actually occurred; cross-racial perceptions are particularly likely to be inaccurate. Even if the initial perception is unadulterated, memory of an event begins decaying immediately, and gaps in memory are often filled with images based on preconceptions and biases, or with post-event information provided by the police or others. Finally, even if witnesses accurately perceive and remember an event, they may have difficulty describing it or be influenced by the manner in which the description is elicited; for instance, a witness may feel compelled to identify someone in a lineup because of conscious or unconscious pressure from the police, the victim, or other witnesses, or because the identification procedure does not provide a “not there” option.

While police and prosecutors can do nothing about perception problems or memory decay, they can minimize the extent to which their actions influence memory, recall, and the ultimate identification.3 Most experts agree that one-on-one confrontations with a suspect should be avoided whenever possible, and that lineups and photo...