M’Naghten Rules:“The jurors ought to be told in all cases that every man is to be presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes until the contrary is proved to their satisfaction; and that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong”.”
The cause of insanity should be defect of reason (R v Clarke  1 All ER 219 Court of Appeal). It should be arising from disease of the mind, which is legal concept not medical one, which means that any disease that affects the way the mind reasons, remembers or comprehends is a ‘disease of the mind’ for the purposes of insanity, and therefore no need of evidence of the impairment of brain. (R v Kemp  1 QB 399).
There are two standards of insanity, the first one is that the defendant lacks of awareness of the physical nature and quality of the act (not its moral qualities). Even if the defendant is aware of the nature and quality of his act, he may still raise insanity in his defence if he does not know that his actions are wrong (legally rather than morally).( RE v Windle  2 QB 526 (CCA))
M’Naghten laid down the common law presumption of sanity. This is a rebuttable presumption of law. If D alleges insanity, then D exceptionally bears the legal burden of rebutting the presumption of sanity and proving his or her insanity on the balance of probabilities (Woolmington  AC 462). If insanity defence succeeds, jury returns a special verdict of ‘not guilty by reason of insanity’ (s74, Criminal Procedure Ordinance) and judge determines the appropriate order to make under s76 CPO.
Note: Insanity is not to deny AR is involuntary, need first got the AR and MR, but negate them all by the insanity defense.
There are two sorts of automatism, insane automatism should follow the M’Naghten Rules of insanity. Non-insane automatism has three requirements: (a). complete loss of control (Broome v. Perkins (1987) 85 Cr App R 321 (DC); Hill v Baxter  1 QB 277 (QBD)); (b). an external cause, such as blows to the head or the introduction of medication (insulin) into the defendant’s system thus give rise to automatism. (R v Quick and Paddison  1 QB 910 (CA)); (c). automatism must not be self-induced. In R v Bailey (John) 1 WLR 760 (CA) failing to eat after taking insulin despite awareness that this could lead to uncontrolled behaviour amounted to self-induced automatism.
The evidential burden is on D to raise issue with a proper evidential foundation (Hill; AG Ref; Bratty). If successful, result is complete acquittal.
Note: automatism deny the AR is not voluntary, no long need to prove MR. As automatism is about not being able to control you action.
Intoxication may be voluntary or involuntary.
Under voluntary intoxication, the defendant has knowingly ingested recreational drugs or alcohol, knowing their nature. Whether voluntary intoxication may be taken into account by law depends upon the nature of the offence he has committed as a distinction is made between crimes of specific and basic intent. The basic intent offence is the offence whose Mens Rea can be either intention or recklessness. The defendant’s intoxication supplies the mens rea of the offence thus the fact of his intoxication combined with the actus reus will establish liability. This common law rule was illustrated in the case DPP v Majewski  AC 443 House of Lords. Majewski is open to criticism because it replaces the mens rea of an offence with abstract recklessness associated with becoming intoxicated. This means that all drunken people will be walking around with the mens rea for all basic intent offences and thus will be liable if they happen to commit the actus reus whilst drunk. On the other hand, the specific intent offence is the offence of mens rea of which is intention only. If the defendant is intoxicated but still able to form the requisite intent, his liability will be unaffected by his intoxication (R v Sheehan and Moore (1975) 1 WLR 739(CA)). But if the defendant is so intoxicated that he is incapable of forming the requisite intent, he cannot be liable (but may be liable for a different offence if there is a basic intent alternative.) (DPP v Beard  A.C. 479).
(Dutch courage)It was held that a person who forms an intention to kill whilst sober and drinks to give himself Dutch courage to do the killing, and who then goes on to kill whilst intoxicated, cannot rely on intoxication to avoid liability. (A-G for Northern Ireland v. Gallagher  AC 349 (HL))
Involuntary intoxication involves non-volitional consumption of drugs and/or alcohol, the use of prescription medication in accordance with instruction or volitional consumption of a non-dangerous drug provided the defendant was not reckless. If effect of non-dangerous drug is merely soporific or sedative, common law position in Majewski does not apply as it is not common knowledge that aggression or danger will result. Common law position only applies if it can be proven that the taking of the non-dangerous drugs was itself reckless, meaning defendant was aware of the relevant risk (R v. Hardie  1 WLR 64 (CA)). And involuntary intoxication only absolves the defendant of liability if it renders him incapable of forming mens rea, not if it caused him to commit an offence he would not have committed if sober.( R v. Kingston  2 AC 355 (HL)).
2,Provocation and Diminished liability—limited to murder (见Voluntary manslaughter)
Provocation and Diminished responsibility, as partial defense, operated to reduce liability from murder to voluntary manslaughter, giving the judge discretion in sentencing as a reflection of the lower level of culpability attached to certain killings.
Provocation is both a common law (R v Duffy  1 QB 63) and statute law defense(Homicide Ordinance (Cap 339) s 4). It has three requirements: (a). There is provocation; (b). D is provoked to lose his self-control; (c). the provocation enough to make a reasonable man do as he did (Holley (2005 PC)). “the reasonable man referred to…is a person having the power of self-control to be expected of an ordinary person of the sex and age of the accused, but in other respects sharing such of the accused’s characteristics as they think would affect the gravity of the provocation to him…” (Camplin).It has been abolished in UK and replaced with the loss of control.
DR is a statute defense (Homicide Ordinance (Cap 339) s 3 Persons suffering from diminished responsibility).It has three requirements:
(a). Abnormality of mind, as illustrated in R v Byrne  2 QB 396 (CCA):”state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal”;
(b). arising from a condition of arrested or retarded development of mind, or any inherent causes or induced by disease or injury. (HKSAR v Liu Chun Yip  HKEC 1616);
Abnormality of mind from self-induced intoxication does not meet the second requirement (Sanderson (1993); Fenton). But if D has a disease of alcoholism, the second requirement may be satisfied if (1) there the alcoholism had caused brain damage; or (2) the intoxication had become involuntary (the person cannot stop drinking)(R v Tandy  Crim LR 308 (CA)). The second requirement may also be satisfied if intoxication present alongside unrelated abnormality of mind.( R v. Dietschmann  1 AC 1209 (HL)). DR will also be available if disease of the mind was caused by long-term illegal drug use (HKSAR v Liu Chun Yip  HKEC 1616)
(c). Substantial impairment of mental responsibility. It can because of inability to understand the nature of his conduct, inability to form rational judgement or inability to control himself (R v Byrne  2 QB 396).
(d). There is a causal link between the defendant’s abnormality of mental functioning and the acts or omissions that caused death, the defendant’s mental impairment will provide an explanation for the killing. The mental impairment must either cause or make a significant contribution to the defendant’s acts or omissions.( R v. Dietschmann  1 AC 1209 (HL))