When is a criminal defendant not mentally competent under the law to continue with their legal case? When is a defendant not responsible for a criminal act based on their mental disease or defect? The answers to these questions–found through assessments of competence to stand trial and criminal responsibility – are key to ensuring that a criminal defendant has the requisite knowledge and skills to participate in their legal case and the mens rea to be convicted of a crime. By applying psychological knowledge to the parameters of the law, forensic mental health experts can assist the legal system to better understand defendants’ current and past mental states and functioning. In order to be capable of doing this properly, the forensic evaluator must have a strong knowledge of the law related to assessment as well as clinical expertise. 

This chapter, geared toward litigators, judges, and forensic evaluators, discusses issues associated with expert testimony related toa defendant’s competence for trial and mental state at the time of a criminal act. This includes the legal framework, approaches to (and the complexities of) clinical assessments, key considerations for evaluators, and common pitfalls in criminal competence, insanity and other mental state assessments. 

Particular topics covered, include: