Where a person uses violence in order to protect themselves or another they may be able to argue that they acted under the common law defence of self defence. Additionally, under s.3 Criminal Law Act 1967, a person can also use reasonable force to prevent the commission of a crime or effect/assist in the lawful arrest of a person. In practice, the common law and statutory defences often overlap because if a person takes out a knife and approaches D, when D reacts by hitting/grabbing their hand to make him/her drop the knife, D is both acting in self defence and acting to prevent a crime.
These are well known defences that receive much publicity, particularly regarding actions of householders who are confronted with intruders. Following public concern after the prosecution of Tony Martin and confusion as to how far people are allowed to use force to protect their homes against burglars, s.76 Criminal Justice and Immigration Act 2008 was passed. This aimed to clarify the common law position; not by changing it but by putting into legislative form some of the legal principles established under the common law.
Where there is evidence of self defence, this must be left to the jury; however there must be evidence on which a jury might think it was reasonably possible that D was acting in self-defence. If it was “a mere fanciful and speculative matter”, the judge may withdraw the defence from consideration. Therefore, the prosecution bears the burden of proof and D the evidential burden and thus compliant with Woolmington .
It is worth noting that the principles of self-defence often protect an individual from ever reaching the court room as the CPS will, using their prosecuting discretion, initially assess whether self-defence applies. If they believe it does, it is unlikely that charges will be brought (such as in Cecil Coley’s case). Therefore, it is only the contentious/questionable cases (i.e. where force was possibly excessive) that do actually reach the court room as a jury is required to assess the applicability of the defence.
Self defence/defence of another are often raised to homicide and non-fatal offences against the person but are not confined to them as they can be raised against a property offence.
s.3 Criminal Law Act 1967 states: “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.”
Thus, this is available to anyone who uses reasonable force to prevent crime or lawfully arrest an individual. For example, if you saw someone ****** a handbag, chased that person and then caught them with a rugby tackle, your action would normally be assault/battery/ABH, but because you were attempting to make a lawful arrest, you should avoid liability.
This term covers self defence, and defence of another. It was generally accepted that self defence was only available where a crime had been/was going to be committed against the person seeking to rely on the defence. However, in Re: A (conjoined twins)  Mary, the weaker twin, was committing no offence herself as she was under the age of 10 and lacked MR. Despite this, Lord Justice Ward stated obiter that the defence should still be available (if it were needed by the doctors) as on the facts, Mary was nonetheless killing Jodie by sharing her heart.
Re: A (conjoined twins) 
Lord Justice Ward: “The availability of such a plea of self defence, modified to meet the quite exceptional circumstances nature has inflicted on the twins, makes intervention by the doctors lawful.”
Necessity of Force
Ds may only rely on these defences if their action was necessary because of a threat of unjustified harm to themselves or someone else, or because of the need to prevent a crime. To decide whether action as necessary, the courts will consider:
- (1) whether D could have retreated from the situation;
- (2) whether the threat was imminent; and
- (3) whether D made some mistake which caused them to think action as necessary.
At one time it was thought that the law required D to retreat as far as possible before resorting to violence. Therefore, if D had the chance to run away but instead chose to fight back, s/he might not have had a defence. This is no longer the case.
R v McInnes  CA: A jury should be directed that, in order for force to be considered reasonable in the circumstances, Ds behaviour should certainly have demonstrated that he did not want to fight, but simply failing to take an opportunity to run away did not in itself make the defence unavailable.
R v Bird  D was at her 17th birthday party when her ex boyfriend (V) arrived with his new girlfriend. D and V began to argue, it became heated, V hit D and she retaliated, lunging forward with her hand which held an empty glass. The glass broke and gouged out his eye. On trial for malicious wounding (s.20 OAPA 1861), the trial judge said D could only rely on self defence if she had shown an unwillingness to fight.
CA: In quashing the conviction they made it clear that this direction “placed too great an obligation” on D. There might be situations when a D might react immediately without retreating and above all it was a matter was for the jury to consider.
2. Imminent Threat
D will only be justified in reacting to a threat which is imminent. This does not mean however that Ds have to wait until they are hit before hitting back, but it does mean that there must be some immediacy about the threat. It is also not necessary for there to be an attack in progress; it is sufficient if D apprehends an attack. Ds can act to prevent force.
R v Beckford 
Lord Griffiths: “A man about to be attacked does not have to wait for his assailant to strike the first blow or fire the first shot; circumstances may justify a pre-emptive strike.”
DPP v Bailey 
Lord Slynn: “Self defence as a concept embraces not only aggressive action such as a pre-emptive strike or aggressive reaction but applies equally to a wholly defensive posture.”
2. Imminent Threat
It follows that it will be lawful for D to use threats of force or even death if that might prevent an attack upon himself or prevent a crime taking place. Additionally, where D apprehends an attack, he may be able to make preparations in order to defend himself even if preparations involve breaches of the law.
Attorney General’s Reference (No.2)  Ds shop had been attacked and damaged by extensive rioting. Fearing further attacks, he made petrol bombs that he intended to use should he face attack in the future. There was no further attack. D was charged with breaching s.4 (1) Explosive Substances Act 1883 for possessing an explosive substance in such circumstances as to give rise to a reasonable suspicion that he did not have it for a lawful object. He pleaded self defence and the jury acquitted. The acquittal was upheld by the CA.
Lord Lane: “There is no warrant for the submission...that acts of self defence will only avail D when they have been done spontaneously. A person may still arm himself for his own protection, if the exigency arises, although in doing so he may commit other offences.”
2. Imminent Threat
AG's reference(No.2) 1983 contrast with:
Malnik v DPP 
D went to visit a man who was believed to have stolen some valuable cars belonging to Ds acquaintance. The suspected thief was known to be violent, so D took with him a rice flail (martial arts weapon consisting of two pieces of wood joined together by a chain.) D was arrested while approaching the man’s house, and the court rejected the argument that carrying the weapon was justified because he was in imminent danger of attack, pointing out that he had himself created the dangerous situation by choosing to go to the man’s house.
The use of any force is not justified if it was not necessary, and this will depend on whether D thought the use of force was ‘subjectively’ necessary. If D makes a mistake which leads him/her to believe there are circumstances making defensive action necessary, courts will assess the necessity of Ds conduct on the basis of the facts as the D believed them to be, even if the mistake was not a reasonable one to make. s.76(4) Criminal Justice and Immigration Act 2008 confirms the common law position that D is entitled to be judged on the facts as he genuinely believed them to be, even if mistaken.
R v Williams (Gladstone)  A man (V) saw a youth trying to rob a woman on the street. He chased after the youth, grabbed him and a struggle ensued. D arrived on scene and, not having seen the robbery, attempted to help the youth who was calling for help. D asked what was happening and V said he was arresting the youth for the mugging (true) and that he was a police officer (false). D asked to see his police warrant card, and when he was not forthcoming, a struggle ensued between the men. V sustained facial injuries, loosened teeth and bleeding gums. D was charged with s.47 ABH and convicted. CA: Quashed the conviction. In deciding whether or not D had a defence, the facts should be treated as he honestly thought them to be. If the man had been attacking the youth, D would have had a defence.
The Privy Council approved of R v Williams (Gladstone)  in Beckford . Thus, if D is walking alone along a road late at night and sees what he thinks is a large man about to attack him with a club, but in reality, D had made a foolish mistake and the ‘large man’ was in fact an elderly woman holding an umbrella, the defence is theoretically available. It follows therefore that D can use force to repel perfectly lawful behaviour, provided D honestly thinks force is necessary. (Remember it is case by case!)
Reasonableness of Force
S.76(6) CJIA 2008 confirms that self defence and the public defence can only succeed if D used reasonable force in the actual/perceived circumstances. This will be a question for the jury who are required to balance the amount of force used against the harm the accused sought to prevent. Therefore, the amount of force considered reasonable for protecting a person might be considered excessive if used to prevent a crime against property.
Strictly speaking, this defence is all or nothing. If force was reasonable, D is not guilty. If force was unreasonable (excessive), D is guilty: this is not a partial defence offering some protection for ‘mostly’ reasonable force. It is critical the jury put themselves in the circumstances which D perceived (reasonably or not, as long as it is genuine).
The law recognises that in the kind of situations where this defence is used, there is rarely much time to consider what should be done.
Reasonableness of Force Cases
Palmer  Lord Morris: “If there has been an attack so that defence is reasonably necessary it will be recognised that a person defending himself cannot weigh to a nicety the exact measure of his necessary defensive action. If a jury thought that in a moment of unexpected anguish a person attacked had only done what he honestly and instinctively thought was necessary that would be most potent evidence that only reasonable defensive action had been taken.”
Whyte  Lord CJ: “...where the issue is one of self defence, it is necessary and desirable that the jury should be reminded that Ds state of mind, that is his view of the danger threatening him at the time of the incident, is material. The test of reasonableness is not...a purely objective test.”
Owino  Collins LJ: “The essential elements of self defence are clear enough. The jury have to decide whether D honestly believed that the circumstances were such as required him to use force to defend himself from attack or threatened attack. In this respect D must be judged in accordance with his honest belief, even though that belief may have been mistaken. But the jury must then decide whether the force used was reasonable in the circumstances as he believed them to be.”
This is an “all or nothing” defence. If excessive force is used, self defence is no longer available.
Lord Morris said that if the prosecution proves that D had used excessive force in self defence, then “that issue is eliminated from the case.” He added that “self defence either succeeds so as to result in an acquittal or it is disproved in which case as a defence it is rejected.”
Therefore, if excessive force is used, the defence will fail. The law imposes an objective test, so it does not matter if D thought they were using reasonable force: what matters is whether objectively they have used a reasonable amount of force.
S.76(3) CJIA 2008 confirms the common law position relating to judging D on the circumstances he believed them to be, that D will not be able to weigh to a nicety the exact measure of force.
R v Anthony Martin 
D lived alone at a remote farmhouse in Norfolk. One night two men broke into Ds house, presumably intending to burgle the property. D was awakened by this and, armed with a pump action shotgun, went downstairs to investigate. There was a dispute about exactly what happened next (was D on the stairs or downstairs waiting for the intruders when he fired), but what was undisputed is that D fired the gun three times; hitting V and W. V was wounded in the legs (Brendan Fearon, 29) and W was shot in the back and died shortly afterwards (Fred Barras, 16). Self defence was left to the jury and rejected. D was convicted of murder and s.18 GBH.
On appeal, his conviction was reduced to manslaughter on the grounds of diminished responsibility. D argued that psychiatric evidence had emerged after the trial showing he suffered from a paranoid personality disorder with recurrent depressive bouts. This still did not however support a plea of self defence.
Following public concern, the Government, the CPS and the Association of Chief Police Officers, jointly published guidance on the subject to make the law clear to the public: Householders and the Use of Force Against Intruders. It stated: “So long as you only do what you honestly and instinctively believe is necessary in the heat of the moment, that would be the strongest evidence of you acting lawfully and in self defence. This is still the case if you use something to hand as a weapon.”
Therefore, even if the intruder is killed, the homeowner will have acted lawfully if force used was reasonable. Conduct which would be viewed as excessive and might lead to a prosecution includes continuing to hurt someone after they are unconscious, and setting a trap. In practice, cases where a householder is prosecuted for using excessive force are rare. According to the CPS, only 11 prosecutions have been brought against people defending their home/premises from burglars, and these included a case where a man laid in wait for a burglar, beat him, tied him up, threw him into a pit and set fire to him, and one where a man repeatedly shot poachers in the back as they fled his land.
R v Clegg ~D was a soldier on duty at a checkpoint in West Belfast one night. A car approached Ds section at speed with its headlights on full and failed to stop. Following orders to stop the car, he and other members of the checkpoint fired at the car. D said he fired 3 times from the front and once from the side of the car as it was travelling towards a fellow soldier as D thought his life needed protecting. (This soldier did have an injury to his foot, suggesting the car drove over his foot, but this injury was later proven to have been caused by someone stamping on his foot, in an attempt to fabricate evidence to support Clegg’s defence.) Forensic evidence showed that while D did fire 3 shots through the windscreen as the car approached, his 4th shot had not been fired from the side, but from behind, after the car had passed and when there could have been no danger. This last shot hit a female passenger in the back and killed her. D was convicted of murder as the last shot was a “grossly excessive and disproportionate” use of force.
Original appeals to the CA and HL all failed but D was released after serving 4 years in prison following campaigns by tabloid newspapers. This caused enormous political controversy: sympathisers argued that British soldiers should not be locked up for ‘doing their duty’ when IRA terrorists were causing much more harm, while those who opposed his release stated that the family of the girl who died were denied justice.
The all or nothing effect of self defence means that where D is charged with an assault but convicted due to excessive force, the judge is able to mitigate the sentence and reflect the need for some force with a more lenient punishment. However, where murder is the charge, there is no such sentencing discretion available to a judge and D will face a mandatory life sentence.
The ‘all or nothing’ effect of self defence prompts many criticisms as a D who rightly thinks force is needed but makes a mistake as to the degree necessary will not be able to rely on the defence. i.e. some force is required but D uses too much. The recent introduction of Coroners and Justice Act 2009 now provides a partial defence (reducing murder to manslaughter) where D kills but uses excessive force. S.54 CJA 2009 provides a defence where D lost self control as the result of a ‘fear of serious violence’, provided that a person of Ds age and sex, with a ‘normal degree to tolerance and self restraint’ and ‘in the circumstances of D’, might have reacted in ‘the same or similar way’.
This offers an alternative defence to Ds in this situation, but only brings the conviction down to voluntary manslaughter rather than the full acquittal that results from successfully raising self-defence.
Intoxication, Mistake and Self-Defence
D can plead self defence even where there was no actual attack provided D genuinely believed he was under attack and force used was reasonable in the perceived circumstances. However, a mistaken belief as a result of being voluntarily intoxicated is no defence. Lord CJ in O’Grady  was concerned that, because self defence is a complete defence, to apply the above principles to intoxicated Ds could mean that dangerous Ds go unpunished. This is now confirmed by s.76 (5) CJIA 2008.
D and V had been drinking heavily when they fell asleep in Vs flat. D claimed he awoke when V began hitting him with a piece of glass. D then picked up an ashtray and hit V, killing him. Lord Lane CJ: “There are two competing interests. On the one hand the D who has only acted according to what he believed to be necessary to protect himself, and on the other hand that of the public and the V in particular who probably through no fault of his own, has been injured, perhaps killed because of the Ds drunken mistake. Reason recoils from the conclusion that ... a D is entitled to leave the court without a stain on his character.”
Intoxication, Mistake and Self-Defence
O'Grady 1987 was confirmed in Hatton  where Ds murder conviction was upheld by CA.
D and V had only met that night at a club and returned to Ds flat. During the evening, V (a manic depressive) had been behaving ‘strangely’, falsely representing himself as an SAS officer, striking martial arts poses and exhibiting a hatred of homosexuals. D claimed to have no recollection of killing due to his heavy drinking, but did claim to have a vague recollection of being involved in an ‘altercation’ with V where he may have then acted in self defence. A stick, which had been fashioned into the shape of a samurai sword belonging to D was found under Vs body, but the murder conviction was upheld.