What is Mens Rea?
The mens rea of an offence is the ‘fault’ element of the offence. It is the defendant’s state of mind or the factors which make him at responsible for his behaviour.
Rules About Mens Rea
The following principles generally apply to attempts to prove or disprove mens rea:
The mens rea must coincide in time with the actus reus: Criminal Injuries Compensation Authority v First-tier Tribunal  EWCA Civ 1554. This means that if the defendant does the actus reus but only forms the mens rea after that act (or vice versa), they will not be guilty of the offence.
If the actus reus can be committed by a continuing act, the defendant need only have mens rea at some point during that act: Fagan v Metropolitan Police Commissioner  1 QB 439.
If the defendant does the actus reus against one person, but had the mens rea with respect to another person, this is sufficient to show an offence: R v Mitchell  QB 741. For example, it is murder to shoot V dead while intending to kill X. This only applies where the defendant has the mens rea for the same crime as the actus reus: R v Pembliton (1874) LR 2 CCR 119. Shooting a dog when the defendant intends to kill a person will not leave the defendant guilty of criminal damage.
Ignorance of the Law
Ordinarily, it does not negate mens rea to show that the defendant did not know that their conduct was illegal: Grant v Borg  2 All ER 257. In other words, a mistake of law will not negate mens rea.
The exception is where the offence makes the defendant’s understanding of his legal rights part of the mens rea. For example, theft requires the defendant to believe the property taken belongs to another. If, due to a misunderstanding property law, he believes the property is his own, he will not have the mens rea for theft.
Impact of Intoxication on Mens Rea
The fact that the defendant was intoxicated when they committed the crime does not, in itself, negate mens rea: DPP v Beard  AC 479. Drunken intent remains intent. Drugs are treated under the same rules if they are well-known to potentially produce unpredictable or dangerous behaviour in the user: R v Hardie  1 WLR 64.
However, intoxication may be relevant evidence as to whether the defendant had the necessary mens rea:
- If the intoxication is involuntary and as a result the defendant did not form the necessary mens rea, he must be acquitted;
- If the intoxication is voluntary and it prevented the defendant from forming the mens rea for a crime of specific intent, then the defendant must be acquitted: DPP v Majewski  UKHL 2;
- Voluntary intoxication is not relevant to proving or disproving the mens rea of crimes of basic intent, by contrast: DPP v Majewski  UKHL 2. It is unclear whether this is a rule of law or merely a rule of evidence. If it is a rule of law, the defendant is assumed to have the mens rea because he is drunk. If it is a rule of evidence the prosecution must still prove the defendant had mens rea. However, the defence would be barred from adducing evidence of intoxication to rebut the prosecution’s case.
There are no definite principles for determining if an offence is one of basic or specific intent. Generally, purposive intention or mens rea going beyond the actus reus makes a crime one of specific intent. Settled categories include:
Crimes of Basic Intent
Assault, battery and sexual assault: R v Heard  3 WLR 475
Section 20 of the Offences Against the Person Act 1861: DPP v Majewski  UKHL 2
Rape: R v Woods (1982) 74 Cr App R 312
The Role of Mistake
If the mens rea of an offence requires the defendant to believe or know a particular fact, then the mens rea will not be established if the defendant mistakenly does not believe in that fact: DPP v Morgan  AC 182. The same is true where the crime requires an intention which logically requires the defendant to believe certain facts. For example, if the defendant shoots a person while believing them to be a mannequin, he cannot have intended harm a human being.
It does not matter that the mistake was unreasonable, unless the offence has an objective or negligence-based mens rea. For example, many sexual offences require the defendant to lack a reasonable belief in that the victim was consenting. For those offences, it does not matter that the defendant mistakenly thought the victim was consenting unless it was reasonable.
Mistake is irrelevant to establishing crimes of strict liability.
Types of Mens Rea
There are two kinds of intention. Either will satisfy the mens rea of an offence which requires the defendant to intend something:
Purposeful intention is where the defendant actively wants to do the proscribed at or bring about the proscribed result: Hayes v Willoughby  UKSC 17.
Oblique intention is where the defendant subjectively knows that the proscribed action or result was a virtually certain consequence of his actions: R v Woollin  AC 82. Mere foresight or recklessness is insufficient.
Knowledge and Belief
Knowledge is defined as true belief, whereas a belief can either be true or false: R v Montila  1 WLR 3141.
For a crime requiring knowledge or belief, it is not enough that the defendant had suspicion or reason to believe. However, if the defendant is wilfully blind to the obvious, this is treated as equivalent to knowledge: Westminster City Council v Croyalgrange (1986) 83 Cr App R 155.
Suspicion and Reasonable Grounds for Belief
Many offences specify a lower standard in relation to the defendant’s knowledge. For example, an offence might require the defendant to have reasonable grounds to believe or to have suspicion.
Suspicion is a subjective state of mind in which the defendant thinks that there is a more than fanciful possibility that something might be the case: R v Afolabi  EWCA Crim 2879.
‘Reasonable grounds to believe/know/suspect’ is a form of mens rea in which the defendant must usually both subjectively suspect/know/believe the relevant thing, and his suspicion must be objectively reasonable: R v Saik  2 WLR 993. There have been some cases where this mens rea has been interpreted as purely objective, however: AB and CD  EWCA Crim 129.
Recklessness is defined as foresight that the proscribed result might come about if the defendant acts as he does or that a particular state of affairs exists. There is no need for the risk to be significant, but it must also be unreasonable for the defendant to take the risk: R v G  UKHL 50; R v Brady  EWCA Crim 2413.
Most offences which have a mens rea of recklessness require that recklessness to be subjective rather than objective: R v Cunningham  2 QB 396. This means that it is not enough that a reasonable person would have foreseen the risk. The defendant must have actually foreseen it himself. Unless an offence says otherwise, it should be assumed that any reference to foresight or recklessness is subjective.
If the crime specifies that the defendant must be negligent, then the prosecutor must prove that a reasonable person in the defendant’s position would not have acted as the defendant did: R v Bannister  EWCA Crim 1571.
This is an objective test. The defendant’s special characteristics and beliefs do not matter unless they are reasonable: R v Colohan (Sean Peter)  EWCA Crim 1251; R v Price  EWCA Crim 229. There is an exception where the defendant is a child – the reasonable person is taken to be the same age as the defendant: R (RSPCA) v C  EWHC 1068.
For strict liability offences, no mens rea is needed at all. The offence is complete once the actus reus is completed. Some crimes have strict liability elements to them without being fully strict liability. For example, assault occasioning actual bodily harm requires mens rea to be shown with respect to the assault but not the occasioning of actual bodily harm.