This chapter explores the ways in which criminal courts have dealt with the emergence of biometrics as a source of evidence. The main purpose in considering this kind of evidence in criminal trials and appeals is to establish the identity of either the offender or the victim. As discussed in previous chapters, fingerprint and DNA analysis have long been admitted as evidence aiding identification, and these have been supplemented more recently by facial and body mapping, voice analysis and other types of biometrics. However, each of these has faced challenges to acceptance as a form of evidence, based mainly on concerns about their reliability, regulatory control and the manner of their presentation in legal proceedings. This chapter provides an insight into the trend of accepting biometric identification as a source of evidence, but with some judicial reservations about the application of particular kinds of biometrics in the criminal justice system. These concerns are largely based on whether certain forms of identification have achieved the degree of scientific reliability that is required for legal admissibility.