The book is intended to be the core text for forensic linguistic courses at undergraduate level, and the key text for postgraduate research students wishing to gain an overall grasp of the subject. The author has based his text on his personal experience as a practising forensic linguist working with lawyers, police and private clients in Britain and the United States.

Forensic Linguistics contains detailed studies of all the major areas of the discipline, including the detection of plagiarism, the observation of style change, and an analysis of all of the most important types of forensic text, including ransom demands, suicide notes, hate mail, smear mail, trick mail, and terrorist mail. Perhaps one of the greatest assets of the book is its discussion of specific forensic texts including the 'stalker text' from John Hinkley, an excerpt from the Unabomber case, several 17th century Salem witch trial 'confessions', Susan Smith's confession, and ransom notes from the Lindbergh kidnapping and Carlos the Jackal's ransom demand at Vienna.

Olsson's main focus is on how forensic linguistics can be of use to law enforcement and criminal justice professionals at the investigation level. This makes the book uniquely authoritative, giving it a practical 'hands-on' appeal to linguists and non-linguists alike. Olsson has worked on civil cases in the UK involving forensic linguistics, and his methods have been quoted in a grand jury hearing in the United States.