Diminished Responsibility

• When a defendant faces a murder charge in court, there are two ‘partial defences’ that can reduce the conviction from Murder to Voluntary Manslaughter, Removing the mandatory life sentence followed by a murder conviction.
• The two partial defences to murder

  • Diminished responsibility
  • Loss of control
• Diminished responsibility - Coroners and Justice Act 2009 s.52


  Must be able to demonstrate...

  1. Abnormality of mental functioning, caused by a recognised medical condition,
  2. Which explains the defendant’s acts or omissions in being party to the killing,
  3. Which substantially impaired the defendant’s ability to:
  4. Understand the nature of their conduct
  5. Form a rational judgement
  6. Exercise self-control
• The burden of proof is on the defendant and the standard of proof is on the balance of probabilities.
• Abnormality of mental functioning

  • Lord Parker defined abnormality as "a state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal"
  • determined by a jury decision, often after hearing medical evidence.
  • must arise from a recognised medical condition.
• Provides An Explanation

  • The abnormality of the mental functioning must provide an explanation for the murder.
  • Can't span from an external factor such as intoxication.
  • However, intoxication doesn't prevent the defence.
  • intoxication can lead to Diminished responsibility due to long-term damage from substance abuse.
• Substantially impairs

  • The defendant’s ability to understand the nature of their conduct, form a rational judgement, or exercise self-control must be “substantially impaired”.
• Impaired meaning 


  • They may still have some ability. They do not have to have lost all ability.
  • Impairment must be more than trivial.
• If a question explains the defendant planned the killing then it may be a sign he is not substantially impaired.
• What type of manslaughter is diminished responsibility

  Involuntary