Law: criminal defences

a selection of cards to help revise for my criminal law exam

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  • Created by: Zoe Dee
  • Created on: 21-01-10 12:36

Defences: Insanity, M'Naghton rules

M'Naghton (1843)- D suffering from extreme paranoia, believed that he was being persecuted by the government. As a result he tried to kill a member (Sir Robert Peel) but instead killed his sectary.
wasn't found guilty of murder but because or his mental state, and was committed to a mental hospital. this was not a result of the verdict and therefore created controversy within the public.this lead to judges being asked to clarify the law in respect of insanity

The answers to these questions have created the M'Naghton rules.

"in all cases every man is presumed to be sane and to posses a sufficient degree of reason to be responsible for his crimes"

For the defence of insanity the D must prove that at the time of committing the act: "he was labouring under such 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 three elements which need to be proved: 1) a defect of reason 2) this must be a result of a disease of the mind 3) this causes the defendant not to know the nature and quality of his act, or not to know he was doing wrong

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Defences: Insanity, defect of reason

Defect of reason

This means that the D's powers of reasoning must be impaired. If D is capable of reasoning but doesn't then this is not defect of reason.

Clarke (1972)- D went to supermarket picked up items and walked out, she claimed she had no recognition of doing the act and therefore did not have the Mens Rea. She said she suffered from absent-mindedness caused my diabetes and depression. The judge said that this meant she was insane. She pleaded guilty to the theft so she didnt go to a mental hospital.

-C of A quashed conviction. M'Naghton rules only applied to people who were unable to reason. Also the rules of insanity don't apply to people who only have moments of confusion or absent mindedness.

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Defences: Insanity, Disease of the mind

Disease of the mind

  • can be mental or a physical disease which effects the mind

Kemp (1956) D suffered from hardening of arteries which caused a problem with supply of blood to the brain. caused him to have moments of temporary loss of consciousness, in which one time he attacked his wife with a hammer. he was found not guilty by reason of insanity even though the problem was not a mental illness

epilepsy- sullivan (1983) suffered from epilepsy, aggresive to people trying to help him, he injured an 80 year old man on one occasion. found not guilty by reason of insanity so pleaded guilty to assault then appealed. H of L ruled that the source of the disease was irrelevant. It could be "organic, as in epilepsy, or functional" and it did not matter whether the impairment was "permanent or transient and intermittent", provided that it existed at the time the D did the act

  • The disease can be of any part of the body provided it has an effect on the mind
  • can be functional- schizophrenia, paranoia, or manic depression
  • can be organic - epilepsy, arteriosclerosis, brain tumours and diabetes
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Defences: Insanity, Disease of the mind (External

Disease of the mind (External factors)

  • where the cause of the D being in a state where he does not know what he is doing is not a disease but an external cause, then this is not insanity

Quick (1973)- D was diabetic who had taken his insulin but had not eaten enough. D was a nurse who assaulted a patient. Not insanity so could rely on the defence of automatism

  • If D has hot taken any drugs (prescribed) and it is the disease causing the problem , then it is an internal cause and it is a "disease of the mind"
  • If D has taken a drug and this is the cause of his automatic state, then this is an external cause and not within the definition of insanity.
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Defences: Insanity, Not knowing

Insanity: Not knowing the nature and quality of the act or not knowing that it is wrong

There are two ways in which the D may not know the nature and quality of the act:

1) because he is in a state of unconsciousness or impaired consciousness ; or

2) where he is conscious but due to his mental condition he does not understand oe know what he is doing.

If D can show either one of these then he satisfies this part of the M'Naghten Rules. The reason for not knowing the nature and quality of the act is because he is an automatic state: Kemp (1956), Sullivan(1983), Henessy (1989), Burgess(1991)

not knowing the act is wrong: Windle (1952)- killed his wife as she constantly talked about committing suicide. "i suppose they will hang me for this" suggests he knew the act was wrong.

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Defences: Insanity: problems with the law

Legal definition of insanity- definition has become a legal one not a medical one this causes two problems:

1) people suffering from certain mental disorders do not come within it; for example, those suffering from irresistible impulses and who are psychopaths (bryne 1960) they know it is wrong but cannot prevent themselves from doing the act

2) those suffering from diabetes, brain tumours or hardening of the arteries are considered legally insane. even sleep-walkers has come within the definition. it is possible to treat these internal cause.


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