Automatism (law)

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Automatism is a rarely used criminal defence. It is one of the mental condition defences that relate to the mental state of the defendant. Automatism can be seen variously as lack of voluntariness, lack of culpability (unconsciousness) or excuse (Schopp). Automatism means that the defendant was not aware of his or her actions when making the particular movements that constituted the illegal act. For example, Esther Griggs in 1858 threw her child out of a first floor window believing that the house was on fire, while having a night terror.[1] Brian Thomas strangled his wife in their campervan in a more recent case in Aberporth in an episode of rapid eye movement sleep behaviour disorder (a disorder related to sleepwalking), where he dreamed there was an intruder on top of his wife. The defence of automatism is denying that the person was acting in the sense that the criminal law demands. As such it is really a denial-of-proof – the defendant is asserting that the offence is not made out. The prosecution does not have to disprove the defence as is sometimes erroneously reported; the prosecution has to prove all the elements of the offence including the voluntary act requirement. Automatism is a defence even against strict liability crimes like dangerous driving, where no intent is necessary.


Automatism is arguably the only defence that excludes responsibility by negating the existence of the actus reus which uniquely allows it to be a defence to both conventional and strict liability offences (although this argument could be extended to the status defence of insanity too). Strict automatism is a denial of actus reus and therefore most commonly used as a defence against strict liability offences. There are a number of reasons why a person may go into a state of automatism, including dissociation or hypo/hyperglycemia.[2] Unconsciousness is the defence of denial of mens rea,[citation needed] which is easier to prove and hence more commonly used for non-strict liability crimes. For example in cases of homicidal sleepwalking the illegal act is typically not denied but the intent to kill is. The defendant will typically be perplexed and confused and will not cover up the episode. Kenneth Parks, after killing his mother-in-law and severely injuring his father-in-law, drove to the police station stating that he thought he'd killed some people. The person's movements seem purposeful - the sleepwalker interacts with his environment in a limited way. Nonetheless the sleepwalker is not conscious of his actions. The use of the term automatism for these situations causes some confusion, as in these cases it is really the lack of intent on the part of the defendant which denies the mens rea of the offence rather than the actus reus (although this distinction is problematic in many instances), better called unconsciousness. Intention is a problem in crimes of strict liability. Very few people intend to crash their vehicles, so clearly something better than intent is required to define automatism.

Another issue with automatism is that when the issue is raised by the defence as a realistic defence (an evidentiary basis), the prosecution then has to prove beyond reasonable doubt that the defendant was acting voluntarily. This is the case for several other defences e.g. duress. The justification for this is that voluntary action is part of the definition of the offence, and therefore something under the presumption of innocence the prosecution has to prove. The evidentiary burden was laid down in Hill v Baxter where the defence of automatism failed because there was no good evidence for the alleged black out. Evidentiary burden means that the defendant needs to provide evidence to satisfy the judge that the issue should be put to the jury, which normally requires medical evidence (although R v Woolley,[3] in which an HGV driver crashed after sneezing, proved an exception).


Because automatism is such a comprehensive defence, there are various exclusions to an automatism defence. The person must not be at fault. The classic example of this is falling asleep at the wheel of a car (Kay v Butterworth). Although one is not responsible for acts done while asleep, one can and is rightly held responsible for driving in a state where one would fall asleep at the wheel. The issue of prior fault applies to many diabetics who suffer hypoglycaemia while driving. Voluntary (and often involuntary) intoxication cannot cause legal automatism.

Causes of insanity will come under the M'Naghten Rules as insane automatism and lead to the special verdict of 'not guilty by reason of insanity' rather than a straight acquittal in sane automatism. The M'Naghten Rules require a "disease of mind", which has been defined in case law as an internal cause. This is medically nonsensical, and does not always bear much relationship to continuing risk which is the main justification. This means that insane automatisms do not require total loss of voluntary control (see below). Thus they are easier to prove in some circumstances, but conversely the burden of proof is on the defendant. Sleepwalking was initially an exception to the internal/external doctrine until the case of R v Burgess.[4]

The most contentious qualifier is that there must be a total loss of control. In Attorney-General's Reference No 2 of 1992,[5] this definition of legal automatism was confirmed. A lorry driver had crashed, and his defence (backed up by expert evidence) was that the monotony of motorway driving had caused him to go into a state of 'driving without awareness' where although he could make minor adjustments to follow the road he was not truly conscious of driving. This followed the decisions of Watmore v Jenkins[6] and Broome v Perkins[7] where diabetic drivers who had driven 3 miles or more were held to not have the total loss of control necessary for the defence of automatism. This definition is problematic, and the Law Commission, Butler Committee and leading legal academic RD Mackay[8] have all argued that this definition is too restrictive.

Classically automatisms in the legal sense have been defined as spasms, reflexes, convulsions or acts committed in a state of unconsciousness e.g. sleep. However there have been cases where the automatism defence was successful when none of these apply. In R v T[9] the defendant had been raped a few days prior to committing a robbery. She was clearly conscious of what she was doing, but in a dissociative state due to post-traumatic stress disorder from being raped. However when Isitt[10] drove away from a collision and evaded a police roadblock in a dissociative state, the defence was not successful. The Canadian court expressed a logical way of distinguishing such cases in Rabey.[11] There the defendant went into a dissociative state due to being spurned. It was held that such a commonplace occurrence was not the sort of external stimulus that would cause legal automatism (although the insanity plea would be open to him).


The problem with omissions and automatism is that the strict legal definition requires total loss of control. A person may well not be able to avoid a crash even though he has some residual control. In this case, the law is imposing liability for failing to do the impossible. Several commentators including HLA Hart[12] have suggested that responsibility for omissions must be framed with reference to the actor's capabilities at the time, rather than the objective test.

See also


  1. Walker, 1968
  2. R v Quick
  3. R v Woolley [1998] CLY 914
  4. [1991] 2 WLR 1206
  5. Attorney-General's Reference No 2 of 1992 [1993] 3 W.L.R. 982
  6. Watmore v Jenkins [1962] 2 QB 572
  7. Broome v Perkins [1987] RTR 321
  8. Mackay, p. 63
  9. R v T [1990] Crim LR 256
  10. (1978) 67 Cr App R 44
  11. (1981) 79 Dominion Law Reports 435 (Ontario Court of Appeal)
  12. Hart


  • Herbert Lionel Adolphus (1968). Punishment and Responsibility: Essays in the Philosophy of Law. Oxford: Oxford University Press. ISBN 0-19-825181-5.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  • Mackay, Ronald D. (1995). Mental Condition Defences in the Criminal Law. Oxford: Clarendon Press. ISBN 0-19-825995-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  • Schopp, R. (1991). Automatism, Insanity and the Psychology of Criminal Responsibility. New York: Cambridge University Press.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  • Walker, N. (1968). Crime and Insanity in England Volume one: The Historical Perspective. Edinburgh: Edinburgh University Press.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

External links

  • Trial of Arnold Burton, 2007: [1]
  • Trial of Brian Thomas, 2009: [2]
  • UK Ministry of Justice consultation, 2012: [3]