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About Fitness to plead 

‘Fitness to Plead’ is a fundamental but understudied concept of criminal justice. It refers to a defendant’s ability to understand and participate in the legal process, a prerequisite to a fair trial. There is a need to balance the individual’s right to make autonomous decisions regarding their trial with their ability to effectively participate. The assessment of fitness to plead is carried out by psychiatrists and determined by a judge, and the costs of dealing with unfit individuals are high. 

Fit for purpose? 

The issue is raised in a small proportion of criminal cases, typically by the defendant’s solicitor, and approximately one hundred defendants are adjudicated unfit to plead in England and Wales annually. This is a startlingly low number considering the high prevalence of mental disorder and cognitive impairment in the criminal justice system, and it is likely that many are not identified. One explanation lies in the antiquated test for determining unfitness, and there is a growing consensus that this should be replaced by a broader test centred on decision-making abilities, or ‘mental capacity’. 

Proposed reforms to the law 

The Law Commission recently acknowledged problems in the current law, and we have contributed to the 2010 Consultation Paper and 2016 Report “Unfitness to Plead” in which many reforms were proposed. These include replacing the existing criteria with a new legal test akin to the civil test for mental capacity, introducing a structured clinical instrument to assess unfitness to plead and screening for unfitness. This would improve fairness in the legal system for vulnerable defendants but is likely to lead to an increase in the number found unfit, placing considerable burden on psychiatric and legal services.  

Our Study 

This project aims to refine our understanding of fitness to plead and address the implications of the Law Commission’s proposals. It aims to determine what the prevalence of unfitness to plead in defendants facing criminal trials would be if those proposals are adopted; the underlying psychiatric and sociodemographic factors that impact on unfitness; and how unfitness should be reliably identified and assessed.  

Development of a Structured Assessment Instrument 

Following a grant from the Nuffield Foundation, we have developed a structured instrument for assessing fitness to plead to be used in research and clinical settings 

Interested in participating? 

If you are interested in participating in the focus groups or would like to know more about the study, please email