Eyewitnesses to crimes provide direct evidence of identification, unlike indirect evidence from DNA or fingerprint matching, and are often indispensable to prosecution services. However, DNA matching of biological material from old cases has also made it clear that hundreds of people have been falsely imprisoned, often based on mistaken eyewitness identifications. There is a long history of research in psychology on eyewitness memory, and this maturing field of research has had recent success applying its findings to public policy and practice. Basic research on eyewitnesses and some practical innovations are discussed in the chapter. These include mining recent advances in memory theory to inform better ways of interviewing witnesses, including those from vulnerable populations, post hoc measurement of the fairness of police lineups, improving ways police lineups are constructed and administered, and testing new methods for constructing police lineups. Some additional topics at the cutting edge of recent research are flagged for the reader, including questions of witness confidence, the advantages of using photo or video lineups over corporeal lineups, and the identification of people from television or photo footage. Critical arguments are also considered regarding the promises and dangers of changing policies and practices based on the research literature.