In their analysis of the role of language in the criminal justice system, authors Lawrence M. Solan and Peter M. Tiersma review a wide array of types of linguistic evidence. The authors point out in chapter 1 that virtually any kind of spoken or written information may be categorized as “linguistic evidence.”
Among the specific kinds of speech and writing they consider, based on use in actual cases, are confessions—both those made by the individual who is later prosecuted and those reported by third parties; the latter are considered hearsay. They address diverse media in which the confessions are recorded, including written accounts, audio recordings, and video recordings. Statements made by the police and by witnesses to a crime are also typically used; these too may be recorded (if at all) in a variety of media.
One of the challenges that the authors discuss is the ways in which particular kinds of evidence are obtained and evaluated. In the case of confessions, for example, the police who obtained the confession may testify that the alleged criminal provided it voluntarily. However, the authors mention several prominent cases, such as the Central Park jogger case, in which it was later decided that confessions were coerced.
When considering speech events, such as an interaction between police and a potential criminal suspect, questions of perception and memory are relevant. The authors point out the issue of consent, such as when an individual in a vehicle supposedly consents for a police officer to search it. When their accounts are considered as evidence, it often becomes clear that one party does not believe they gave consent or does not remember doing so, while the other is convinced that the suspect did so.