What is Automatism? A Legal Defence Explained

Automatism is a legal defence used when someone acts without conscious control. If proven, it can remove the required intent (mens rea) needed for a crime. In strict liability cases, it challenges whether the act (actus reus) was voluntary, essentially arguing that the person did not commit the act deliberately.

This defence is particularly relevant in cases involving road traffic accidents, where a sudden and total loss of control can lead to catastrophic or even fatal consequences. For example, medical episodes such as an epileptic fit or a hyperglycaemic attack (when blood sugar levels become too high) could form the basis of an automatism defence.

The Legal Basis of Automatism

Automatism is not written in law but is a legal defence based on past court cases.  The leading case on the matter is Bratty v Attorney General for Northern Ireland [1963], where Lord Denning described automatism as:

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“An act which is done by the muscles without any control by the mind, such as a spasm, a reflex action, or a convulsion; or an act done by a person who is not conscious of what he is doing."

 

There are two main types of automatism: insane automatism and non-insane automatism. The distinction is crucial, as it determines the outcome of a case and the available defences.

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1. Insane Automatism

Insane automatism occurs when the loss of control is caused by an internal factor—a condition legally referred to as a disease of the mind. If a person’s actions arise from such a condition, they may be considered legally insane, and the defence falls under the insanity defence rather than automatism.

Examples of insane automatism include conditions such as epilepsy, sleepwalking, or certain psychiatric disorders. If this defence is successful, the verdict is not a straightforward acquittal but rather a special verdict of “not guilty by reason of insanity”. This can result in hospital orders or other court-imposed restrictions, rather than outright freedom.

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2. Non-Insane Automatism

Non-insane automatism occurs when the loss of control is caused by an external factor. If a person’s actions were completely involuntary and not due to their own fault, they may be fully acquitted.

Unlike insane automatism, a successful non-insane automatism defence leads to a full acquittal rather than a special verdict. However, the defence is only available if the loss of control was both unforeseen and not self-inflicted.

For example, a driver who falls asleep at the wheel due to fatigue cannot use this defence, as they should have either avoided driving altogether or stopped as soon as they began feeling drowsy.

How is the Automatism Defence Proven?

To raise the defence of automatism, the defendant must provide initial evidence. In cases involving medical conditions, expert medical evidence is typically required.  The court will then determine whether the automatism was insane or non-insane:

• If the defence is insane automatism, the burden of proof is on the defence, which must prove insanity on the balance of probabilities (i.e., more likely than not).

• If the defence is non-insane automatism, the burden of proof remains on the prosecution, which must prove beyond reasonable doubt that the act was voluntary. If the defence raises any reasonable doubt, the prosecution’s case will fail.

 

Challenges of Relying on Automatism

The term "insanity" can be problematic because it carries a stigma, which may discourage defendants from using the defence. Instead of a full acquittal, a successful insanity defence results in a special verdict, which can lead to medical detention or supervision. Additionally, the defence is hard to prove because the loss of control must be complete. If the person had any awareness or control, the defence is unlikely to succeed.

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A complex but important legal defence 

Automatism is a complex but important legal defence that recognises that people can sometimes act involuntarily due to medical conditions or external factors. The distinction between insane and non-insane automatism is critical, as it determines whether a defendant receives a full acquittal or a special verdict of insanity.

While this defence can provide relief for those who truly had no control over their actions, proving automatism requires strong medical or evidential support. If you or someone you know is facing charges where automatism may be relevant, it is essential to seek specialist legal advice to ensure the best possible outcome.

If you need legal guidance on automatism or any other defence, feel free to contact us at LMP Legal. Our expert team is here to help.