Special Defences to the Non-Fatal Offences Against the Person
Consent as a Defence to Assault and Battery
Effective consent (whether express or implied) is a complete defence to a charge of assault or battery.
Some argue that the absence of effective consent is part of the actus reus of those offences, not a defence. For these notes, it will be treated as a defence.
There is also a defence if the defendant honestly believed that the victim consented. There is no need for that belief to be reasonable: DPP v Morgan  AC 182; R v Kimber  3 All ER 316.
Consent might be implied from the victim’s words or behaviour. It will also be implied where the victim engages in activities which carry an obvious and normal risk of touching. For example, touching is a natural result of moving through a crowd. People are also normally held to implicitly consent to being touched to get their attention: Wiffin v Kincard (1807) 2 Bos & PNR 471.
However, people are not taken to implicitly consent to the risk of actual violence or unreasonable touching simply because they accept they are taking the risk of that violence: H v CPS  All ER (D) 56.
When is Consent Effective?
Consent is only a defence if it is effective. The following factors are relevant to establishing that the victim’s consent was effective:
The Victim’s Capacity
The victim must be capable of giving valid consent, which might not be the case if the victim is young, unconscious, drunk or mentally ill. Children in particular must be ‘Gillick-competent’: Gillick v West Norfolk and Wisbeck AHA  AC 112.
The Victim’s Knowledge
The victim’s consent is not valid unless they understand the broad nature and purpose of the act and the nature and seriousness of any risks involved: R v Konzani  EWCA Crim 706.
Fraud and Deceit
Historically, fraud or deceit would only negate the victim’s consent if it relates to the nature of the act or the defendant’s identity: R v Richardson  2 Cr App R 200. It is possible that broader frauds can now vitiate consent after the advent of the Sexual Offences Act 2003, as the Court of Appeal in R v Richardson  QB 444 stated that the rules on when consent is vitiated should not differ depending on whether the assault is sexual or not.
The threat of physical violence, dismissal from employment or criminal prosecution are all examples of duress which will vitiate the victim’s consent to force: R v McCoy (1953) (2) SA 4 (AD). It is not clear whether the threat must be one a reasonable person would have succumbed to or how grave the threat must be.
Consent as a Defence to Offences Causing Harm
As a general rule, consent is not a defence to any offence which causes ABH or worse: R v Brown  UKHL 19. The courts recognise some categories of activity as allowing the defence of consent even if it causes harm, however:
People can validly consent to the risk of harm which arises out of the normal play of any widely accepted sport R v Bradshaw (1878) Cox CC 83. This includes boxing and martial arts, where harm is intentional, but not unregulated fighting: R v Brown  UKHL 19.
Consent to medical and cosmetic surgery is a defence to any non-fatal offence against the person: R v Brown  UKHL 19.
Consent is a defence to injuries caused by rough play if the defendant did not have intention to cause harm: R v Brown  UKHL 19.
Hair-cutting, piercings and tattooing are all exempted forms of body-modification which consent can apply to. More niche forms of body-modification, such as tongue splitting, do not tend to fall within this exception: R v BM  EWCA Crim 560.
The right to engage in religious flagellation and circumcision was acknowledged in R v Brown  UKHL 19.
Consent to take the risk of harm is valid: R v Slingsby  Crim LR 570. This includes the risk of sexually transmitted disease if the victim is fully informed of the risk: R v Dica  EWCA 1103.
Defences Relating to Children
Lawful Chastisement of a Child
It is lawful for a parent to commit a battery or assault against a child to punish them. However, the punishment must not be done for gratification or out of anger, must not be done with unsuitable instruments, go beyond the child’s ‘powers of endurance’ or be calculated to endanger life or limb: R v Hopley (1860 2 F&F 202.
This is not a defence to acts which cause actual bodily harm or worse, however: Children Act 2004, s 58. The defence is also unavailable to school teachers. However, school teachers have a defence where they are seeking to avert physical injury or property damage: Education Act 1996, s 548.