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All offences, with the exception of those which are strict liability, require a prosecution to prove, as part of their case, that the defendant had the requisite mens rea, or criminal mind, required to commit the offence in question. This usually means proving intent or recklessness as to the actus reus. For example, to prove battery, a prosecution must prove that the defendant applied physical force to the victim and that he either intended to, or was reckless as to that application of force. Sometimes the actus reus and the mens rea do not need to correspond with each other; that is what this page will examine.
The correspondence principle
According to Glanville Williams, correspondence, as illustrated by crimes such as criminal damage, battery and causing grievous bodily harm with intent, is a subjectivist ideal. Many crimes breach this principle. Murder requires either an intention to kill or an intention ‘merely’ to cause grievous bodily harm, and unlawful act manslaughter can be committed with the mere intent to commit a battery, for example. Horder attempts to explain this divergence with his ‘proximity principle’ which stressed moral fault.
Crimes of negligence
Some offences use an objective mens rea as opposed to a subjective mens rea, arguably removing the requirement of a state of mind altogether. Rape is a good example of this; a jury is only asked to decide objectively whether the defendant had a reasonable belief of consent; what the defendant actually believed at the time is irrelevant. This is in line with B v DPP , where Lord Nicholls stated that the more serious an offence is, the more there is a presumption of the defendant’s guilty mind.
Fortunately, there is one caveat to most objectively judged mentes reae: a requirement that the defendant was able to perceive a relevant risk. Often, it is said that an objective mens rea test should take into account the surrounding ‘circumstances’, in an attempt to circumvent the disadvantage a defendant is put at. In R v G , two boys were not convicted of causing criminal damage as they were unable to perceive the risk of the damage being caused. Unfortunately, R v B  left open what scope ‘circumstances’ has, leaving the test quite uncertain.
DPP v Morgan ‘s subject test of consent in sexual offences was replaced by an objective test in the Sexual Offences Act 2003, however, the case has been applied in other contexts. The Queen v Beckford , for example, provided that self-defence should be purely subjective judged. R v Caldwell  has now also been overruled, but in the opposite way, by R v G , replacing an objective test of recklessness with a subjective one.
Unless a lack of mens rea is intended by Parliament, courts will read in mentes reae into offence. Sweet v Parsley  is a good example of this. This is despite the fact that strict liability offences were originally developed by judges. Strict liability, as can be seen in R v G  (a different case to R v G ), often reverses the rule of presumed innocence until proven guilty, but the ECHR said in Salabiaku v France  that it would not interfere with national laws of strict liability.
The leading case on strict liability is Gammon v A-G of Hong Kong , where the Privy Council stressed that a presumption of innocence may only be displaced if there is a social concern such as public safety. In true crimes, the presumption should push the other way, towards a mens rea requirement, although the definition of a true crime is undefined and it seems false to advocate fairness where the defendant received a 3 year prison sentence via a strict liability offence.
Strict liability and offences with a mens rea requirement are opposites. Simester and Sullivan perhaps adequately summarised that negligence is a good half-way house: objectivity in the circumstances. However, Sweet v Parsley  rejected this suggestion.