Defences to Criminal Charges

Defences to Criminal Charges

Mental Illness

– Prove that at the time the accused was unsound of mind

– If found not guilty then the accused by have to be admitted to a mental institution

– R v Porter (1936)

Self defense

– Proved that he/she was acting to defend themselves

– Knows that it was wrong

– Only used whatever force was reasonably necessary eg. not stabbing someone 2000 times

– Zecevic v DPP (1987)


– Necessary to avert serious danger

– Must be in proportion to the danger

– Compulsion: they were compelled/forced to act criminally due to other circumstances

– R v Dudley and Stephens (1884)


– Knows it was wrong

– he/she was so frightened by threats of death or serious bodily harm that he/she committed the act

– Can be complete or a partial defence

– Compulsion: they were compelled/forced to act criminally due to other circumstances

– R v George Palazoff (1986)


– Acted with the victim’s consent

– Often reduces liability

– Consent must be ‘freely and voluntarily’ given

– R v Mueller (2005)

Partial defences reduce the liability of the defendant from (usually) murder or manslaughter


– Claims he/she was aggravated by the victim in such a way that the action of the murdered person would have caused an ordinary person to lose self-control

– The Queen v Damian Karl Sebo (2007)

Substantial impairment of responsibility // Diminished responsibility

– Claims they were not in complete control of him/her mind when they committed the murder

– Chayna v The Queen (1993)


  • Mental Illness
    • The defence must prove that the accused was mentally unstable at the time of the act; therefore they did not have the proper mens rea.
    • The offender is not released, but put under supervision in a mental health institute.
  • Self Defence
    • Makes provision for people to defend themselves, but states that they may not use greater force than is reasonably necessary.
    • Excuses the defendant from the crime, as it would have been necessary for them to stay alive.
  • Compulsion – Necessity
    • Necessity is available where the circumstances induce the accused to break the law to avoid even worse consequences.
    • Therefore, breaking the law is a better outcome than not breaking the law
  • Compulsion – Duress
    • When the accused claims that they were forced to act due to threats of death or serious injury to themselves, or other people.
    • This defence is not available in NSW for those committing murder in the first degree, though people who assisted in the crime may use this defence.
  • Consent
    • This defence is used most commonly in sexual assault cases.
    • The prosecution must prove there was a lack of consent in the case.
    • Consent is unsubstantial if given from a child, or people under the influence of drugs or alcohol


  • Provocation
    • The activity of one person that causes another person to lose control of their actions.
    • Must be shown the victim provoked the accused’s criminal behaviour.
  • Substantial Impairment of Responsibility
    • Exists when a person suffers from an abnormality of the mind that impairs their mental responsibility
    • Easier to prove than insanity, as the mental disorder can be less severe (e.g. intoxication, drugs etc)


Extract from Legal Studies Stage 6 Syllabus. © 2009 Board of Studies NSW.