Linguists are frequently asked to help the police and courts when there is a dispute over the authorship of a written text -- suicide note, abusive or threatening letter, email or text message. In this excerpt from his inaugural lecture, Professor Coulthard explains the concepts he used to help identify the authorship of text messages in a recent murder trial. The full lecture is available online at: http://streaming.aston.ac.uk/communications_ram/Inaugral_lecture_malcolm_coultard.asx Aston University is home to the world's first centre for forensic linguistics. Find out more at: www.aston.ac.uk/forensic-linguistics