Will you stand up in court? On the admissibility of psychiatric and psychological evidence

The courts' general approach to psychiatric and psychological evidence is reviewed and an alternative reading of Turner [1975], the leading case on the admissibility of such evidence, is proposed. It is argued that in order to be an effective forensic practitioner the mental health professional needs to be apprised of the criteria used by courts to determine the admissibility of expert evidence. These criteria are illustrated by considering a recent Court of Appeal case in which psychiatric evidence tendered by the defence was excluded. Three essential qualities of admissible expert evidence are identified and explained, namely the evidence must: 1) fall squarely within the boundaries of the witness's expertise; 2) on balance, afford practical assistance to the court; and 3) defer to the values, objectives and priorities of criminal proceedings, as structured by substantive criminal law.