UCL Faculty of Laws


Laws Open Day taster session - Criminal Law



"It is a general principle of criminal law that a person may not be convicted of a crime unless the prosecution have proved beyond reasonable doubt both (a) that he has caused a certain event or that responsibility is to be attributed to him for the existence of a certain state of affairs, which is forbidden by criminal law, and (b) that he had a defined state of mind in relation to the causing of the event or the existence of the state of affairs. The event, or state of affairs, is called the actus reus and the state of mind the mens rea of the crime." Smith & Hogan, Criminal Law

Therefore the elements of crime are separated into:

  • I.  Actus reus - the culpable act, and
  • ii. Mens rea - the required mental state
  • (iii. the absence of a valid defence)


Conduct must be voluntary in the sense of a `willed action': an accused should not be culpable for an act (even though it is his act) over which he has no control.

Bratty v A-G for Northern Ireland [1963] AC 386, HL, 409

" The requirement that it should be a voluntary act is essential, not only in a murder case, but also in every criminal case. No act is punishable if it is done involuntarily:” (per Lord Denning)


Bratty v A-G for Northern Ireland (supra)

" …an involuntary act in this context - some people prefer to speak of it as automatism - means an act which is done by the muscles without any control by the mind such as a spasm, a reflex or a convulsion; or an act done by a person who is not conscious of what he is doing such as an act done suffering from concussion or whilst sleep-walking" (per Lord Denning)

Hill v Baxter [1958] 1 QB 277, 286

“A person who is attacked by a swarm of bees while driving and as a result is no longer able to control the vehicle, may be held to be no longer ‘driving’, i.e. an essential part of the actus reus is no longer present as it has ceased to be voluntary action.

Bell [1984] 3 All ER 842

“a motorist (who) has been attacked while driving by, for example, a swarm of bees or a malevolent passenger, or because he has been affected by a sudden blinding pain, or because he has become suddenly unconscious by reason of a blackout, or because his vehicle has suffered some failure, for example, through a blow-out or through the brakes failing” (per Lord Goff)

Burns v Bidder [1967] 2 QB 227

If a person is acting in a 'non-voluntary' or 'automatic' state and as such there is no actus reus, he is not culpable. Proof of such automatism leads to acquittal.


Bratty (supra)

“It seems to me that any mental disorder which has manifested itself in violence and is prone to recur is a disease of the mind. At any rate it is the sort of disease for which a person should be detained in hospital rather than be given an unqualified acquittal” (per Lord Denning in Bratty)

Sullivan [1984] AC 156, HL

Quick [1973] 1 QB 910

“A malfunction of the mind of transitory effect caused by the application to the body of some external factor, such as violence, drugs, including anaesthetics, alcohol and hypnotic influences cannot fairly be said to be due to a disease”

Hennessey [1989] 1 WLR 287

Burgess [1991] 2 QB 92, CA

“it seems to us that if there is a danger of recurrence that may be an added reason for categorising the condition as a disease of the mind. On the other hand, the absence of the danger or recurrence is not a reason for saying that it cannot be a disease of the mind.”(per Lord Lane C.J. in Burgess)

Pooley (Aylesbury Crown Court, 16 Jan 2007, unreported)

Thomas (Swansea Crown Court, 12 Jan 2007, unreported)

Emlyn (Dolgellau Magistrates Court, 8 March 2011) unreported)

“psychological blow”/ dissociative state

Hennessey (supra)

T [1990] Crim L.R.256

[Rabey (1977) 37 Canadian Criminal Cases 461 – “the ordinary stresses and disappointments of life which are the common lot of mankind do not constitute an external cause…”]

Other areas? Hypnosis? Allergy?


Bratty v A-G for Northern Ireland (supra)

" The term 'involuntary act' is, however, capable of wider connotations: and to prevent confusion it is observed that in the criminal law an act is not to be regarded as an involuntary act simply because the doer does not remember it. ...Nor is an act to be regarded as an involuntary act simply because the doer could not control his impulse to do it." (per Lord Denning)

Total loss of voluntary control

Broome v Perkins (1987) 85 Cr.App.R. 321

AG Ref (No 2 of 1992) (1993) 97 Cr App R 429


“...if it was the defendant’s own fault that brought on the involuntary conduct or the resultant harm, the law will not allow him to escape liability by sheltering behind the facade of automatism. Thus even though a person’s conduct might actually be involuntary at the time he caused the harm, he will nevertheless be held liable if it was his own fault he got himself into that situation...such a defendant is ‘at fault’ in bringing about his state of automatism when he does something (such as taking a drug) or fails to do something (such as fail to eat after taking insulin) and he knows, or ought to know, that there is a risk of resultant involuntary conduct.” (Clarkson, Understanding Criminal Law)

Lipman [1970] 1 QB 152
Bailey [1983] 1 WLR 760
Quick (supra)
Marison [1996] Crim LR 909