I. Criminal responsibility

1. Actus reus - the doing of a prohibited act.

2. Mens rea - the guilty mind (intention).
THE HARLOT'S CASE (1560); DPP v. MORGAN (1975); WOOLMINGTON v. DPP (1935)
- Where an offence is made 'absolute', a crime is punishable in the absence of mens rea.
- However, the defendent must have had the means of knowing.
SWEET v. PARSLEY (1970)

II. Exemptions

1. Mistake
a) Lack of knowledge of facts is a defence:
R. v. HIBBERT (1869); R. v. PRINCE (1875); R. v. MILLER (1975)
b) Mistake of law is no defence ('ignorantia juris haud excusat'). But this rule is sometimes relaxed where ignorance is inevitable - i.e. a statute not having been made public.

2. Duress - either physical compulsion or threat.
a) Available in respect of all crimes except murder.
b) The accused must have acted as a person of reasonable self-control would have done.
c) There is no defence when a person knowingly enters into affairs where pressure to commit a crime is likely - i.e. joining a street-gang.
d) A wife may (still) escape responsibility for a crime (other than treason or murder) committed in the presence of her husband if she invokes 'coercion'.
e) 'Superior order' (military etc.) are not likely to be a good defence.

3. Self-Defense
a) The success of the defence will depend upon whether the degree of force employed was reasonable in the circumstances. The following case was, although today it would be reversed, one of self-defence:
R. v. HUSSEY (1924)
Moments of extreme danger may justify the instinctive taking of measures which, apart from the agony of the moment, would otherwise be unreaonable.
b) A mistake about whether there is an unlawful attack may provide an excuse for an otherwise unlawful act.
A mistake about the degree of the force necessary will not excuse if it be induced by voluntary intoxication.

4. Necessity
This is rarely a defence - there being little authority for it. Denied in:
R. v. DUDLEY AND STEPHENS (1884)


III. Incapacity

1. Unsoundness of mind
a) Insanity
aa) During custody, the Home Secretary is entitled under the provisions of the Mental Health Act 1983 to detain the accused in a mental hospital.
bb) The accused may be found unfit to plead (admission to a mental hospital [always in murder cases] or order of guardianship, supervision of treatment or an order of absolute discharge).
R. v. JUDITH WARD (1974)
cc) As a defence to a crime
R. v. M'NAGHTEN (1843)
- every person is presumed to be sane until the contrary is proved.
- It is a defence to prove that, at the time of the commission of the act constituting the offence charged, the accused was labouring under such a defect of reason, from disease of mind,
- as not to know the nature and the quality of his act,
- or (if he did know the latter), as not to know that what he was doing was wrong.
- Where the accused suffers from such insane delusion as to the surrounding facts, which conceals from him the the true nature of the act he is doing, he is under the same degree of responsibility as if the facts were as he imagined them to be.
- where insanity is pleaded the defence must establich on a balance of probabilities that the accused was insane.
b) Uncontrollable impulse is not recognized as a defence. But proof of it may be relevant to insanity.
c) Mental abnormality as to diminish responsibility.
- It was introduced by the Himicide Act 1957 as a defence to a murder charge having the effect of reducing the conviction to one of manslaughter.
- It must be proven, on a balance of probabilities, that the accused was suffering from such abnormality of mind as to substantially impair his mental responsibility for his acts and omissions in doing or being a party to the killing.
d) Automatism - only if there is total destruction of voluntary control (trance, administration of insuline).

2. Drunken persons
a) Excessive drunkenness may induce actual disease of the mind, as in the case of delirium tremens. Here, the M'Naghten may apply.
b) Proof of drunkenness (inducing a state of mind falling short of insanity) may server to negative the existence of some particular kind of intent necessary for the establishment of guilt - i.e. malice aforethought, which is an essential element
in the definition of the crime of murder.
c) If the accused first has formed the intent to kill, then got drunk to carry it out, there will be no defence (a.l.i.c.).
d) Where the fact of drunkenness is of itself the essence of a charge, the is no defence under those principles.

3. Minority
a) Kids under ten cannot be held guilty of a crime.
b) Kids aging ten to 14 are presumed to be incapable of forming criminal intent.

4. Corporations
a) Under the old common law, corporations could not be held liable for crimes.