Chapter 14 notes the extensive range of biometric traits that can be used to seek to identify or differentiate between individuals. Details of some relevant technologies are given and pertinent legal issues are considered. Military uses of biometric data are explained, noting e.g. that biometric processes are likely to be the means of enabling autonomous targeting of individuals. Control of access, determining whether a person has an offensive intent and identification of criminal suspects are among the most likely applications of biometrics in the civilian context. A core challenge is adherence to data protection requirements, the relevant aspects of which are teased out. Particular issues arise in relation to criminal suspect identification and these are set forth. Legal considerations arising from the ICCPR, the American Convention on Human Rights and under the General Data Protection Regulation are addressed at some length and the implications of the Fourth Amendment to the United States Constitution are noted. Comparisons are then made between the military and peacetime applications of the technology and the associated law and in a concluding section biometrics is set in the context of other novel and emerging technologies.