In Abdul-Hussain, the court stressed that the threat of death or serious injury had to be imminent. The threat must be of immediate harm so that defendant could not reasonably be expected to take evasive action. If this was the case, the defendant did not intend to harm the victim, but rather his purpose was to avoid the threat being carried out.  INSANITY Under the British justice system, defendants could use insanity as an excuse only if they had mental defects that prevented them from being able to know right from wrong when they committed a crime.
 Under the McNaghten's Rules, the insanity defence is available to a defendant who can prove that at the time of his or her offence, he or she was suffering from a 'defect of reason', caused by 'disease of the mind'. The phrase 'disease of mind' means that defendant must show that he was suffering from a disease which affected the functioning of the mind.  This rule states that insanity is an excuse when the sufferer did not know the nature or quality of the action taken or did not know that it was wrong.
 This may arise where the defendant had no awareness of what was happening or where the defendant was aware of what he was doing, but was deluded as to the material circumstances of his actions, rendering the act fundamentally different. It is even so where a person was unaware of the consequence of his act.  'Wrong' here means that the act was illegal; the defendant must not know that his actions were legally wrong. In Windle, Lord Goddard held that "wrong" means contrary to the law, and not "wrong according to the opinion of the man".
It is the reason that insanity involves a particular kind of blindness or ignorance that makes insanity to be regarded as an excuse. In addition, another reason that the insane criminal has an excuse is because that his or her action was not voluntarily undertaken. Criminally insane are to be excused because they are mentally diseased; more particularly, because their actions were the 'product' of a disease.  Legal insanity is an excuse that also permits inquiry into a defendant's capacity to know the law or to exercise free will. It focuses on the individual's personal characteristics rather than the situation in which she acts.
 If a person pleads "not guilty by reason of insanity" (NGRI), that plea means that the person had committed the underlying criminal act, but, because of mental illness, should not to be held responsible for that act.  PROVOCATION Provocation is a 'concession to the frailty of human nature'.  In English common law, this defence is satisfied only where the killing is founded on moral indignation or outrage, and, in more recent times, the result of an uncontrolled rage following trivial and, more latterly, grave provocation.  (a) The 'reasonable excuse' view
The provocation excuse should be a concession to extraordinary external circumstances.  The view is that a defendant who acts having lost of self-control is not fully responsible for his action.  Stanley Yeo suggested that this test of 'loss of control' requires that the provocative conduct creates in the accused intense anger, panic or fear.  When provocation has led to great anger, the excusatory focus is the all-too-human characteristic tendency to act in a spontaneously retaliatory fashion.  Anger diminishes self-control.
 While anger, a person's state of mind is not within control and hence it is said that having killed in the heat of the moment are less culpable. 'The defence of provocation is for those who are in a broad sense mentally normal' but who snap under the weight of very grave provocation.  Where a perpetrator feels anger and suffers loss of self-control to the provocation situation, he should be afforded a defence of provocation. However, in the face of similar provocation, the perpetrator ought not to act in worse a way than the reasonable man would have done.
(b) The 'justification' view It is plausible to judge cases of provocation that the appropriate expression of anger, for those who have suffered severe provocation, might involve some minor violent outburst. For instance, a mother who is told by another that he has raped her child would at least be justified in displaying some anger or outrage for this might be an appropriate manifestation of her anger towards him. In hitting and slapping him she might be entitled to a justification defence. If she kills him on the other hand, it might be argued that she has an excuse.
 Her action was inappropriate but it was reasonably close to the violent response that would have been justified in the face of severe provocation. The justification ought to go not to the action itself but rather to the loss of self-control.  DIMINISHED RESPONSIBILITY AND INTOXICATION Where persistent substance abuse has given rise to brain damage or psychosis on the part of D the court in Tandy and Inseal accepted that alcoholism is a disease falling within section 2 of the Homicide Act 1957.
This mean that a state of intoxication brought on by alcohol could, in the case of an alcoholic be a foundation for a finding of substantial impairment of responsibility. However, this will only be the case if the consumption was "involuntary".  Involuntary intoxication occurred where the D is unaware of the intoxicant because it is secretly concealed in a soft drink, administered without consent, the result of automatism or the unforeseen effect of medication.  In Kingston, the court ruled that D was not responsible for an indecent assault he had perpetrated as he was involuntarily intoxicated.
WITHDRAWAL BY A SECONDARY PARTY The law has always recognised that a person who has embarked on a criminal enterprise may withdraw from it and save himself from a criminal liability in respect of it. The modern law on withdrawal was addressed in Becerra and Cooper where Roskill LJ stated that an effective withdrawal must: "serve unequivocal notice on the other party to the common unlawful cause that if he proceeds upon it he does so without the further aid and assistance of those who withdraw".
These principles were followed in O'Flaherty, and in this decision Mantell LJ held that, 'a person who unequivocally withdraws from the joint enterprise before the moment of the actual commission of the crime, here murder, should not be liable for that crime'. The Law Commission has suggested that in the case of assistance such a defence should only be available if the secondary party takes all reasonable steps to prevent the commission of the crime he has assisted.
Where the accused decides to withdraw long before the commission of the offence, a defence should be afforded where he makes it very clear to the others that any further activity will go ahead without assistance from the accused. Where the offence is about to be committed the defence should be afforded where the accused try to prevent the commission of the offence by force if necessary. CONCLUSION As Paul Robinson has stated: 'an actor's conduct is justified; an actor is excused'.
It is said that to amount to a justification so that a defence will be afforded, the defendant must have both guiding and explanatory reasons for being justified, and the guiding reason must correspond with the explanatory reasons.  While excused is analogous to justification, excuses excuse the act or omission amounting to wrongdoing, by shedding favourable moral light on what D did through focus on the reasons that D committed that wrongdoing, where those reasons played a morally 'active role' in D's conduct.
 Where a perpetrator either a principal of secondary offender is able to prove that his act is either justified or excused, there is strong reasons that a defence should be afforded.
Books Fletcher, GP, and JD Ohlin, Defending Humanity: When Force is Justified and Why? , Oxford University Press, New York, 2008. Gardner, J, 'Justifications and Reasons', Oxford University Press, Oxford, 1998, pp. 118-122. Hart, HLA, Punishment and Responsibility: Essays in the Philosophy of Law, Clarendon Press, Oxford, 1968. Herring, J, Criminal Law, 3rd edn, Oxford University Press, New York, 2008.