A person can become a witness to a crime in many ways, from being present at a minor altercation to being the bank cashier during an armed robbery. In an investigation, each witness may have important details of the event that may help the authorities apprehend the suspects and mount a prosecution. Witnesses may provide information in a number of ways. Apart from interviewing (see Chapter 6), police may ask witnesses to help generate images of suspects or identify an offender from an identity parade of possible suspects. In court, lawyers may ask the witness to repeat their testimony under oath, ask him questions or cross-examine him to identify weaknesses in his account of events. This chapter considers how attentional and memory process may affect a witness’s capacity to give accurate testimony through weapon focus, the misinformation effect and the effects of emotional arousal. Finally, the special problems posed by child witnesses and the use of likenesses and identity parades are discussed.