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Public and Private Defences - Self -Defence and Prevention of Crime
Public and private defences cover the common law defence of self-defence, prevention of crime under the Criminal Law Act 1967 and the protection of property under the Criminal Damage Act 1971. The basic premise of public and private defences is that it is, in some circumstances,  lawful to use reasonable force in self-defence, prevention of crime or to damage property for the protection of other property.  Therefore self-defence and prevention of crime act to negate an element of the actus reus of the offence rather than operating as true defences. Recently,  the Criminal Justice and Immigration Act 2008 has clarified some of the legal principles which emerged from case law and put them on a statutory footing. This was a consolidating measure and the Act did not seek to change the existing law.
Public and private defences cover
  • Self-defence at common law



The defence in relation to criminal damage is considered in the Criminal Damage lecture.  There is an overlap with self-defence and prevention of crime in that when a person is acting in self-defence, they are generally preventing a crime being committed on themselves and therefore s.3 Criminal Law Act may be used. It is only where the attacker lacks capacity or has a defence that the common law of self-defence needs to be used. For both self-defence and prevention of crime the requirements are the same. That is that the force used must be reasonable in the circumstances. S. 3. Criminal Law Act 1967 provides that a person may use such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders or of persons unlawfully at large. At common law self-defence also requires the force to be reasonable in the circumstances. The burden of proof lies on the prosecution to establish that the level of force was unlawful, that is excessive, in the circumstances.
Reasonable force
S.76 Criminal Justice and Immigration Act 2008 puts the common law of reasonable force on a statutory footing. It applies where a person is relying on self-defence, or s.3(1) of the Criminal Law Act 1967. S.76 is a consolidating section. Its purpose is merely to clarify the existing law. it does not seek to change the common law as is made clear in s.76(9). The question of whether force used is reasonable contains both subjective elements and objective elements.
Reasonable force - subjective element
S.76(3) Criminal Justice and Immigration Act 2008 provides that the question whether the degree of force used by D was reasonable in the circumstances is to be decided by reference to the circumstances as D believed them to be. This is thus decided subjectively. S.76 (4) provides further guidance on the application of this question:


 If D claims to have held a particular belief as regards the existence of any circumstances—

(a) the reasonableness or otherwise of that belief is relevant to the question whether D genuinely held it; but

(b) if it is determined that D did genuinely hold it, D is entitled to rely on it for the purposes of subsection (3), whether or not—

(i) it was mistaken, or
(ii) (if it was mistaken) the mistake was a reasonable one to have made.
This affirms the law as established in the following cases: 
R v Gladstone Williams (1984) 78 Cr App R 276 Case summary
Beckford [1987] 3 WLR 611 Case summary
S.76(5) upholds the rule in O Grady that where the mistaken belief that they were acting in self-defence is attributable to voluntary intoxication, the defendant is unable to rely on the mistaken belief.
R v O'Grady [1987] QB 995 Case summary

Where the person is actually under attack there should be no direction to the jury based on intoxicated mistake:
R v McGrath [2010] EWCA Crim 2514  Case summary
S.76(6) provides that the degree of force used in self-defence or prevention of crime by the defendant is not to be regarded as having been reasonable in the circumstances as D believed them to be if it was disproportionate in those circumstancesS.76(7) provides further guidance stating that a person acting for a legitimate purpose may not be able to weigh to a nicety the exact measure of any necessary action; and evidence of a person’s having only done what the person honestly and instinctively thought was necessary for a legitimate purpose constitutes strong evidence that only reasonable action was taken by that person for that purpose.
Reasonable force - objective element
Whilst the question of reasonable force is decided by reference to the circumstances the defendant believed them to be the level of force is decided objectively.
Initially a subjective test was applied for self-defence and prevention of crime:
R v Scarlett [1993] 4 All ER 629  Case summary 
However, this position was considered unsatisfactory and was changed to an objective test:
R v Owino (1996) 2 Cr App R 128  Case summary
This was affirmed in R v Martin where the court rejected the question of taking into account the characteristics of the defendant in assessing whether the level of force was reasonable in the circumstances for the purposes of self-defence:
R v Martin [2002] 2 WLR 1  Case summary
There is no longer any duty to retreat in order to rely on self-defence see:
R v Julien (1969) 1 WLR 839  Case summary 
R v Cannes (1971) 1 WLR 1600 Case summary
R v Bird [1985] 1 WLR 816 Case summary
Where the defendant is the aggressor or deliberately provokes the victim into punching him, self-defence will only be allowed where the violence offered by the victim was so out of proportion to that offered by the defendant, that in effect the roles were reversed:
R v Keane [2010] EWCA Crim 2514  Case summary
The defences of self-defence and prevention of crime can be used to cover preparing for attack:
Excessive force and murder
There have been some calls for a change where self-defence fails in relation to a murder charge due to excessive force. The argument is that in such cases the jury should have the option of returning a verdict of manslaughter rather than having the all or nothing approach of murder or no criminal liability at all. The cases of Tony Martin and  R v Clegg (Case summary) have fuelled such debate. Such an approach was adopted in Australia in the case of The Queen v. Howe 100 C.L.R. 448 (Case summary) but was subsequently abandoned. Such an approach was rejected by the Privy Council in R v Palmer (1971) AC 814 (Case summary).
Public and private defences of self-defence, prevention of crime or protection of property