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The defence of insanity 

When should a person not be criminally liable because of a mental condition at the time they committed an alleged offence? 

Problem (Back to top)

The current rules that govern the “insanity defence” (also referred to as “insane automatism”) date from 1843. They have been widely criticised for a number of reasons: 

  • it is not clear whether the defence of insanity is available in all cases; 
  • the law lags behind psychiatric understanding, and this partly explains why, in practice, the defence is underused, and medical professionals do not apply the correct legal test; 
  • the label of “insane” is outdated as a description of those with mental illness, and simply wrong as regards those who have learning disabilities or learning difficulties, or those with epilepsy; 
  • the case law on insane and non-insane automatism 1 is incoherent and produces results that run counter to common-sense. 

The empirical data suggest that the defence of insanity is successfully raised in only a small number of cases. 

The Law Commission has worked in this area before. In July 2012 we published a scoping paper in which we asked questions to discover whether the current law causes problems in practice, and if so, the extent of those problems. The responses to that paper informed a Discussion Paper, published in 2013. 

In the Discussion Paper, we set out provisional proposals for reform of the defences of insanity and automatism, based on lack of capacity, and explained how they would work with the law on intoxication. 

However, we did not continue with this work, prioritising instead the logically prior work on unfitness to plead. 

Project (Back to top)

Taking our Discussion Paper as its starting point the project will consider when a person should not be criminally liable because of a mental condition at the time they committed the alleged offence. 

This project forms part of the Law Commission’s 14th Programme of Law Reform. 

Next steps

The Law Commission will commence work on the project as soon as resources allow. 

Further steps and their timings will be confirmed in due course. 

Documents (Back to top)

There are no documents published as part of this project currently. 

Updates (Back to top)

There are no updates on this project currently. 

Contact (Back to top)

Contact us if you have any queries about this project. 

Email: Criminal@lawcommission.gov.uk