Defences- Insanity

Revision cards for the defence of Insanity

  • Created by: Jack
  • Created on: 29-11-12 14:18


M'Naghten Rules

1.Defect of reason

2.Caused by a disease of the mind

3.That results in the defendant not knowing the nature or quality of thier acts or that it is wrong

Burden of Proof

1. Always on the D claiming insanity

2.  On the 'Balance of Probabilties'

3. If found to be an insane verdict will be 'not guilty by reason of insanity'

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Insanity 2

Not used for cases of Strict Liabilty

DPP v H (1997)
The D was driving whilst intoxicated and tried pleading insanity

Defect of Reason

  • D's abilty to reason is altogether impaired

Clarke (1972)

  • Defect of reason must be more than mere 'absent-mindedness or confusion'
  • D went into supermarket and was charged with theft of mincemeat
  • She said she did not even like it
  • Trial Judge allowed a verdict of insanity caused by diabetes and depresson
  • The COA overturned the verdict and said that 'defect of reason must only be aplied to those that have a disease of the mind and not confusion or absent-mindedness
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Insanity 3

Disease of the Mind

  • Legal term and not a medical one
  • Can be physical or mental as long as it affects the mind

Kemp (1956)                                                             

  • Suffered from hardening of the arteries              
  • Caused temporary loss of consciousness
  • Attacked his wife with a hammer
  • GBH s.20 OAPA 1861
  • Not guilty by reason of insanity
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Insanity 4

Sullivan (1983)

  • Defendant suffered form epilepsy
  • Visited an 80 year old neighbour and had a fit and injured the man
  • HOL overturned conviction and allowed plead of insanity
  • HOL said 'source of disease does not matter and that it can be permanent or transient and intermittent, providing it happended at the time D carried out the act' 
  • Extended the meaning of insanity

Hennessy (1989)

  • Defendant was a diabetic
  • Had not taken insulin for 3 days
  • Seen getting into a car and driving off with no recollection
  • The disease of diabetes can affect the mind
  • He could plead insanity


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Insanity 5

Burgess (1991)

  • D attacked his girlfriend whilst asleep
  • No evidence of an external cause
  • Judge ruled it was an internal cause;sleep disorder
  • Not guilty by reason of insanity

External Factors
In order to plead insanity D must be suffering from an internal factor

Quick (1973)

  • D was a diabetic and did take insulin but not eaten enough
  • Caused low blood sugar levels which affected brain
  • Assaulted a patient
  • Could not claim insanity as the cause was external in this case the drug insulin
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Insanity 6

The Effect of Quick

  • Diabetics who have not taken insulin can be regarder as insane
  • Diabetics who have taken insulin but not eaten enough may not plead insanity

Not Knowing the nature of the act/ whether it was wrong

1. State of unconsciousness
2. Being conscious but not knowing what they're doing is wrong

Defendants in an automatic state

Kemp (1956) - blocked arteries/hammer attack
Sullivan (1983) - eplilepsy/attack
Hennessy (1989) - diabetic/stole car
Burgess (1991) - sleepwalker/attacked girlfriend

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Insanity 7

Knowing that it is wrong

  • Only legally wrong
  • Even if they got a mental illness they must not think that they are 'legally wrong' in order to claim insanity

Windle (1952)

  • D's wife wanted to commit suicide
  • He gave her 100 aspirins
  • He killed her but wqas mentally ill
  • But when he rang the police he said 'I suppose they'll hang me for this'
  • Could not plead insanity as it proved he knew he was legally wrong
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Insanity 8

Johnson (2007)

  • D forced into his neighbours flat and stabbed her
  • At his trial 2 phychiatrists gave evidence he was suffering from paranoid schiozophrenia and hallucination
  • But they said he knew what he was doing was legally wrong

Problems with law on insanity

1. Legal Definition
2. Overlap with automatism
3. The position of diabetics
4. The decision in Windle
5.Social Stigma
6.Proof of insanity

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Insanity 9

Legal Defintion

  • Legal rather than medical one
  • Some mental disprders do not come within it e.g. physchopath
  • Not in M'Naghten Rules because they what they are doing is legally wrong
  • Whereas those suffering physical illness have been allowed to plead insanity e.g. Hennessy, Kemp and Burgess 

Overlap with automatism

  • If disease puts D in automatic state rather than an external factor they can use insanity
  • Those who use automatism receive a full acquittal whereas for insanity the judge must place an order on them
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Insanity 10

The position of diabetics

  • Some fall within or not depending if they have not eaten and taken insulin or just not taken insulin
  • Those who have not eaten and taken insulin plea for automatism and get a full acquittal for the offence

The decision in Windle

  • A D who is suffering from a reconised mental illness and who does not know that thier act is morally wrong can plead insanity
  • Cannot plead insanity if they know that their act is legally wrong

Social Stigma

  • No-one wants to be claimed insane
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Insanity 11

Proof of Insanity

  • Burden of proof is on the D
  • Possible breach of Article 6 ECHR
  • Jury should not decide whther they agree D is insane
  • Should be left to medical experts
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