The insanity defence in the UK is a legal defence that allows a defendant to be found not guilty of a crime if they prove their insanity at the time of the offence. The basis of the insanity defence is the M’Naghten Rule, which was established in 1843. Following the insanity defence defined under M’Naghten Rule, the following are the key factors and elements of consideration for insanity in any legal case in the UK:

Reduced Mental Capacity 

Being medically insane and legally insane are two different things. In UK law, the jury decides on the basis of simple rules of interpretation, procedure and evidence, therefore, it is legal insanity – not medical insanity. The UK court has dealt with a variety of mental states when dealing with the question of a disease of the mind.

For instance, in one case, a person with arteriosclerosis presumably had a disease of the mind, even if there were differing medical opinions. Moreover, in another case a diabetic who didn’t take insulin and committed a crime was also found to have a disease of the mind.

Capacity to Reason Properly

For the defence of insanity, the disease of the mind must result in a defect of reason. This means the defendant either didn’t know what they were doing or didn’t understand that their actions were wrong. Simply being forgetful or confused is not enough. The crucial factor is the loss of their ability to reason properly.

Awareness of the Wrong Act 

For an insanity defence, it’s fundamental that the defendant was not aware their actions were against the law. The term “wrong” here refers to not morality but legality. If the defendant knows what they did was legally wrong, the insanity defence won’t work.

For example, in a specific case a defendant admitted that he gave his wife a deadly dose of aspirin but later expressed awareness that he might get punishment for it. The court rejected his insanity plea because there wasn’t enough evidence to support it. The Court of Appeal clarified that “wrong” in this context means acting contrary to the law. Since the defendant was aware of this, the insanity defence was invalid.

Insanity Defence Reforms Under the Criminal Procedure Act 1964

The Criminal Procedure (Insanity) Act 1964 is an Act of Parliament of the United Kingdom that amended the law on the insanity defence. The Act was passed in response to concerns that the M’Naghten Rules were too narrow. Secondly, the rules did not adequately take into account the defendant’s mental state at the time of the offence. 

The act states that; If a defendant claims insanity during the trial, it depends on if they can understand the charges, the difference between “guilty” and “not guilty,” and can communicate with their lawyers. Inability to do the above deems them “unfit to plead” under the Criminal Procedure (Insanity) Act 1964, Section 4. 

In such cases, the judge has broad discretion on how to handle the defendant, except in murder cases where the defendant must be kept in a hospital. The Act remains in force today and it is the main piece of legislation governing the insanity defence in the UK.

Final Thoughts

Criminal cases that involve insanity defence can be very complicated. Therefore, at Concise Medico our vetted panel of expert witnesses understand the responsibility of giving an impartial testimony in such cases.  

If you are stuck in a case where the defendant had plead for insanity defence, reach out to our forensic psychology or psychiatry experts today! Concise Medico has the largest panel of HCPC-registered medical expert witnesses. Contact us today and have the best expert lead your case and get you closer to justice. 

Share This Article!