This paper describes the content of the 2019 British Academy of Forensic Sciences (BAFS) biennial Ormrod Lecture, which took place at Guy’s Hospital Tower, London, on 17 October 2019. This lecture is traditionally given by the outgoing President of BAFS, on this occasion Dr Meng Aw-Yong, who presented issues relating to acute behavioural disturbance and deaths in police custody.