Criminal Law: Insanity

Insanity

Establishing Insanity

Insanity is a defence which has three elements: M’Naghten [1843] UKHL J16

  1. At the time of the commission of the offence, the defendant was suffering from a ‘defect of reason’;
  2. This defect of reason was due to a disease of the mind; and
  3. The defect rendered the defendant unaware of act’s nature and quality or made him unaware the act was ‘wrong’.
A ‘Disease of the Mind’

Diseases of the mind do not necessarily line up with what medical professionals would call mental illness. It covers any internal medical condition which produces defences of reason, including from physical illnesses: R v Sullivan [1984] AC 156; R v Kemp [1957] 1 QB 399. External causes, by contrast, are excluded and may only be subject to the defence of automatism.

Diabetes: Note that hypoglycemia (too little sugar from an insulin overdose) is an external cause. Hyperglycemia (too much sugar from taking insufficient insulin) is an internal cause. Contrast R v Hennessy [1989] 1 WLR 287 with R v Quick [1973] 3 WLR 26.

Nature and Quality of the Act
yelling, delusion, hallucination

This limb of the third requirement of the insanity defence applies where the defect of reason leads the defendant to not realise what he is physically doing: R v Sullivan [1984] AC 156. For example, if the defendant hits the victim thinking he is knocking a vase over, this limb would apply.

Appreciating Wrongs
legal, illegal, wrongs, understanding

This limb of the third requirement of the insanity defence applies only where the defendant believed he was acting legally: R v Johnson [2007] EWCA Crim 1978. This includes cases where the defendant falsely believed he had a defence (e.g. self-defence) because of a delusion: M’Naghten [1843] UKHL J16. If the defendant knew his acts were illegal, however, his appreciation of morality is irrelevant. This is true even if he was acting in accordance with an ‘irresistible impulse’: R v Kopsch (1925) 19 Cr App R 50.

Insanity, Negligence and Strict Liability

The defence of insanity is available even if the offence is one of negligence or strict liability: Loake v CPS [2017] EWHC 2855.

The Effect of Establishing Insanity

If the defence of insanity is established, the defendant is found not guilty by reason of insanity. While they are considered not guilty, they may still be subjected to incarceration under a hospital order: R v Birch [1990] 11 Cr App R (S) 202.


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Criminal Defences Quiz

Test yourself on the principles governing when a defendant has a defence to a criminal charge.

1 / 31

Micah is charged with stealing drugs from a pharmacist. They rely on the defence of duress, arguing that they were under the threat of serious injury or death as they were withdrawing heavily from medication at the time. Is the defence likely to succeed?

 

2 / 31

Omar takes prescription medicine for depression. One day, he has a rare reaction to the medicine which causes him to involuntarily commit a criminal offence. The prosecution argue that he cannot rely on the defence of automatism, because he voluntarily took the medicine which caused the automatism. Will this argument succeed?

 

3 / 31

Ellen is 17 years old but suffers from a developmental disorder which gives her the emotional maturity of a 7 year-old. Can she escape liability on the grounds that she lacks criminal responsibility?

 

4 / 31

For the purposes of the defence of insanity, a disease of the mind may be caused by any internal or external trigger. True or false?

 

5 / 31

Celestine owes a loan shark, Mia, a lot of money. On Sunday night, Mia tells her that if Celestine does not pay her back by Monday morning she will kill her daughter. Celestine tries to get help from the police, but they tell her they do not believe her. Celestine then robs a local corner store to get the money to pay back Mia, but is caught soon after and arrested. Can Mia rely on the defence of duress?

 

6 / 31

Is duress a defence to murder?

7 / 31

When establishing the defence of duress, what three elements must exist before the impact of the threat on the defendant is considered sufficient?

8 / 31

People are under a duty to retreat rather than use force in self-defence is they are able. True or false?

 

9 / 31

What are the two elements of the defence of persons defence?

10 / 31

Celestine owes her drug dealer, Mia, a lot of money. On Sunday night, Mia tells her that if Celestine does not pay her back by Monday morning she will kill her daughter. Celestine tells her she does not have the money, so Mia tells her to mug Richard as he carries a lot of money on him at all times. Celestine tries to get help from the police, but they tell her they do not believe her. Celestine robs Richard, but is caught soon after and arrested. Can Mia rely on the defence of duress?

 

11 / 31

Is the defence of necessity available to an offence of strict liability?

 

12 / 31

Lucy, Theo and Marius were trapped in a sinking ship. To buy time pending the arrival of a rescue vessel, Lucy threw Theo overboard. Theo drowned. Lucy has been charged with murdering Theo. She proves that if she did not kill Theo, the ship would have sunk and she and Marius would have died. Can she rely on the defence of necessity?

 

13 / 31

Can the defence of self-defence be relied on if the defendant provoked the victim to attack?

14 / 31

Atticus gets extremely drunk at a party, and commits an offence as a result. He claims the alcohol made him act involuntarily, and advances the defence of automatism. Will his defence succeed?

 

15 / 31

Celestine is driving when she feels the onset of a hypoglycemic episode. She is not able to pull over in time before the episode starts. She is barely in control of her body, but is able to move the steering wheel a little and as a result is able to avoid hitting pedestrians. She eventually collides with a tree. Can Celestine rely on the defence of automatism in relation to any criminal offence she is charged with?

16 / 31

Josephine commits a crime involuntarily because of a hypoglycemic episode. Which defence would you advise her to rely on?

17 / 31

What three elements must the defendant show to rely on the defence of automatism?

18 / 31

Can an adult be convicted of being an accessory to a crime committed by a child under the age of criminal responsibility?

 

19 / 31

Insanity is not a defence to an offence of negligence or strict liability. True or false?

 

20 / 31

What are the two elements of the defence of insanity?

21 / 31

Can the defence of self-defence be relied on where the force is used pre-emptively?

22 / 31

Micah mistakenly believes that Joseph is threatening to kill her unless she robs a bank. Can she rely on her mistaken belief to establish the defence of duress?

23 / 31

For the purposes of the defence of insanity, a disease of the mind includes mental illnesses and not physical illnesses. True or false?

 

24 / 31

When determining whether a sober and reasonable person would have succumbed to a duress, what characteristics of the defendant is the hypothetical person given?

25 / 31

Moira, a teenager, joins a local gang to obtain protection against bullies at school. She knows that the gang have engaged in violent robberies in the past, but the gang leader promises her that they will not involve her in these as she is too young. The gang later threatens to cripple her mother if she does not hold onto a package of drugs for them. Can Moira rely on the defence of duress when charged with drug possession?

 

26 / 31

What are the three elements of the defence of duress?

27 / 31

What is the age of criminal responsibility in England and Wales?

28 / 31

What three elements must be shown to establish the defence of necessity?

29 / 31

Josephine commits a crime involuntarily because of a hyperglycemic episode. Which defence would you advise her to rely on?

30 / 31

Leo is trying to escape a burning building. The only way out is up a ladder, but that ladder is being blocked by Gareth. Gareth is frozen in fear and cannot move out of the way to let Leo pass, nor can he move up the ladder. Because they will both die if Leo does nothing, Leo pulls Gareth off the ladder, causing him to fall to his death. He is later charged with Gareth's murder. Is the defence of necessity available to him?

 

31 / 31

When establishing self-defence or defence of others, can the defendant rely on any mistaken beliefs as to the circumstances that are the result of his being voluntarily intoxicated?

 

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