For the majority of offences, there are two elements of an offence which require the prosecution to prove beyond a reasonable doubt – the actus rea (the act) and the mens rea (the specific state of mind related to the incident in question). The exceptions are crimes of strict liability, where only the actus rea requires proving (for example, speeding).

The test for the mental element is specific to the offence; examples include recklessness, intent for a specific act, a reasonable belief, or foreseeing an outcome.

Whether a person did in fact form the mens rea (mental element) for the crime is for the court to determine, but medical evidence may be put forward regarding the defendant’s capacity to form the mens rea for the offence. This is one of the few defences that may be available to defendants who were intoxicated at the time of the offence. Crimes have been broadly split into those of basic or specific intent, which governs whether intoxication is able to be used as a defence via incapacity to form the mental element.

• Involuntary intoxication may be relevant to crimes of specific or basic intent, if it has removed the ability to form the required mental element of the offence.
• Voluntary intoxication may only be relevant to crimes of specific intent.

The definition of a crime as of basic or specific intent is not obvious or consistent, and reference to the law for that specific crime is required.  The test for the mental element should be provided by the instructing lawyer.

Crimes of specific intent have been held to include:

• Murder
• 18 wounding/GBH with intent
• Arson/criminal damage with intent to endanger life

Crimes of basic intent have been held to include:

• Common assault
• 47 assault occasioning actual bodily harm
• Manslaughter
• Assault on a police officer in the execution of his duty
• 20 wounding/GBH
• Taking a conveyance without the owner’s authority
• Arson/criminal damage
• Arson/criminal damage being reckless as to whether life would be endangered
• Sexual assault (despite the fact that “intentional” touching of the complainant by the defendant is an essential element of the offence)

The courts have formulated two categories of drugs: ‘dangerous’ and ‘non-dangerous’: R v Bailey [1983] 2 All ER 503; R v Hardie [1985] 3 All ER 848. Knowingly taking a ‘dangerous’ drug counts as voluntary intoxication. Knowingly taking a ‘non-dangerous drug’ may also count as voluntary intoxication, depending on the subjective appreciation of the likely effects of the drug in the quantity and circumstances in which it was consumed.

“…the Valium was taken for the purpose of calming the nerves only, that it was old stock and that the Appellant was told it would do him no harm. There was no evidence that it was known to the Appellant or even generally known that the taking of Valium in the quantity taken would be liable to render a person aggressive or incapable of appreciating risks to others or have other side effects such that its self-administration would itself have an element of recklessness. It is true that Valium is a drug and it is true that it was taken deliberately and not taken on medical prescription, but the drug is, in our view, wholly different in kind from drugs which are liable to cause unpredictability or aggressiveness. It may well be that the taking of a sedative or soporific drug will, in certain circumstances, be no answer, for example in a case of reckless driving, but if the effect of a drug is merely soporific or sedative the taking of it, even in some excessive quantity, cannot in the ordinary way raise a conclusive presumption against the admission of proof of intoxication for the purpose of disproving mens rea in ordinary crimes, such as would be the case with alcoholic intoxication or incapacity or automatism resulting from the self-administration of dangerous drugs.”

Involuntary intoxication:

1. May be accepted where a drug has an unexpected result to that anticipated: R v Hardie [1985] 1 WLR 64
2. Ignorance of the strength or effect of a drink or other intoxicating drugs that a defendant has voluntarily consumed, does not make the subsequent intoxication involuntary: R v Allen [1998] Crim. L.R. 698 CA
3. Is not a defence where the mens rea was formed: a drunken/drugged intent is still an intent: Kingston [1995] 2 A.C. 355

Kingston and his victim were drugged by a third party, and Kingston then sexually assaulted the victim. It was found that though the involuntary intoxication may have removed his inhibitions, he was still able to, and did, form the required mental element for the offence.

Voluntary intoxication:

1. Only relevant to crimes of specific intent: DPP v Beard [1920] AC 479; DPP v Majewski [1977] AC 443 HL
2. A drunken intent is still an intent: R v Sheehan and Moore (1975) 60 Cr App R 308
3. Intoxication for ‘Dutch courage’ to commit an offence, cannot form the basis of a defence: AG for Northern Ireland v Gallagher [1963] AC 349.
4. May extend to the ‘immediate and proximate consequences’ of intoxicants, beyond the intoxication stage: R v Taj [2018] EWCA Crim 1743

Taj mistook an innocent man for a terrorist and attacked him, in the context of paranoia subsequent to recent cannabis use. This case expanded the definition of “attributable to intoxication” to encompass the “immediate and proximate consequences” of substance misuse, including the induction of poor mental health. Though it was noted in the judgement that this conclusion “does not extend to long term mental illness precipitated (perhaps over a considerable period) by alcohol or drug misuse”.

The Law Commission: Intoxication and Criminal Liability 2009