Murder and the mental state of the defendant.

The early episodes of The Detectives: Murder on the Streets show the Manchester Major Incident Team painstakingly assemble evidence that will be used to support the prosecution case for the murder of Daniel Smith.

Daniel had been brutally attacked in a make shift homeless camp situated under railway arches in Manchester. As the narrative unfolds it becomes clear that Spice, a form of synthetic cannabis, had been widely used by members of the homeless community living at this site, as well as by those who are suspected of involvement in the attack. The implication is that those who are responsible for Daniel’s murder may have acted under the influence of this potent psychoactive substance.

To understand how the law treats defendants who perform criminal acts whilst under the influence of substances that effect their mental state it is helpful to tease out the elements of criminal liability. To be found guilty of murder it must be shown that a defendant has carried out both the relevant physical action, in addition to having the relevant state of mind. Lawyers often use the Latin phrases actus reus (guilty action) and mens rea (guilty mind) as short hand for this principle. To be guilty of murder a defendant must have both the relevant actus reus (causing the death of a human being) and the relevant mens rea (either the intention to kill, or the intention to cause serious harm).

Courts have long wrestled with the issue of how to treat defendants who have performed the actus reus, but whose mental state has been affected by illness or intoxication, or most perhaps even a combination of both.

Can it be a defence to a charge to murder to argue that the defendant didn’t intend to kill or harm the victim, but acted as they did because they were under the influence of alcohol or a drug like Spice?

The mental state of a defendant

The law does recognise that there are circumstances when, even though a defendant has performed an act that would normally be considered criminal, they should not be convicted of any offence. For example if a defendant’s action is entirely involuntary she may rely on the defence of automatism. Automatism will only work as a defence to a criminal charge if the defendant has acted without any consciousness of what is being done and is therefore performed involuntarily. Examples include involuntary actions resulting from concussion after a blow to the head, involuntary movements of an anaesthetised patient or the effects experienced by a diabetic who fails to eat after taking insulin.

However if the action results from a ‘disease of the mind’ then the related defence of insanity may apply, as provided by the Trial of Lunatics Act 1883 . Although a successful defence of automatism will result in an acquittal, if defendant is found not guilty by reason of insanity the court has the authority to detain the defendant for treatment for their mental illness. Insanity has been used as a defence where defendants have been suffering from conditions which impact upon mental functioning such as schizophrenia, epilepsy and even sleepwalking.

Voluntary Intoxication

Although the law is sympathetic to defendants who act without the required mens rea, due to mental conditions for which they are blameless, it takes a less than sympathetic view to defendants who impair their mental state by voluntary intoxication through drink or drugs.

Obviously allowing criminal acts to go unpunished merely because a defendant was acting under the influence of drink or drugs would not be in the public interest. However, in some circumstances, voluntary intoxication can reduce the level of criminal liability. This is because voluntary intoxication can work as a defence to crimes of specific intention.

Most criminal offences are offences of basic intent, which means that the mens rea requires either an intention or recklessness to cause the prohibited outcome. A specific intent crime is one where recklessness is not sufficient for the mens rea. Murder is an example of a specific intent crime as the mens rea requires either an intention to kill, or an intention to cause serious harm.

Therefore if a defendant charged with murder can show that, due to taking drink or drugs, she was unable to form the intention to kill or cause serious harm then voluntary intoxication could be used as a defence. However, in such circumstances it is likely that the defendant would still be guilty of manslaughter.

Critics argue that the current state of the law in this area is confusing and is ripe for reform and modernisation. The Law Commission have begun the process of reviewing this area of law and have published several documents on the work they have conducted so far, which is an excellent place to start if you would like to learn more about how a defendant’s mental state can impact on their criminal liability.

Hugh McFaul is a Lecturer in The Open University Law School and is interested in the intersection between law and religion, legal ethics and public legal education. This article was previously published in October 2017 on OpenLearn. You should subscribe to our newsletter for more free courses, articles, games and videos.



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