Diminished Responsibility and the Criminal Law – Homicide Act & the Coroners and Justice Act

Diminished Responsibility

What is meant by Diminished Responsibility?

Diminished is one of three special defences which exist for the criminal offence of murder. The defence of diminished responsibility is set out in Section 2 of the Homicide Act 1957 as amended by the Coroners and Justice Act 2009. When the defence is successfully pleaded it has the effect of reducing a murder conviction to manslaughter.

Diminished responsibility is part of three special defences which differ from all other defences in the criminal law as they do not apply to all crimes – only applying to murder – and that they have the effect of reducing criminal liability rather than absolving the defendant from liability completely. Also contained within this three pronged group are the defences of provocation and suicide pact.

Requirements for Diminished Responsibility

Section 2 of the Homicide Act, as amended by the Coroners and Justice Act, sets out the three requirements which must be established by the defendant in order to succeed with the defence of diminished responsibility. The three requirements are as follows:

  1. There must be an abnormality of mental functioning  
  2. This abnormality of the mind must have been caused by a recognised medical condition
  3. The abnormality of the mind must substantially impair the defendant’s mental responsibility 

Abnormality of mental functioning

Homicide Act versus Coroners and Justice Act

The previous law under the Homicide Act stated that the defendant must be suffering from an abnormality of the mind whereas the amendment made by the Coroners and Justice Act states that the defendant must be suffering from an abnormality of mental functioning.

In order to establish whether a defendant is suffering from an abnormality of the mind medical evidence will be provided in court and it will be up to the jury to decide whether the defendant is in fact suffering from that.

The medical evidence is simply opinion, albeit it given by a medical professional qualified and often specialising in that field, and the jury is not bound to follow it. Ultimately it is the final decision of the jury as to whether the defence of diminished responsibility should succeed.

The test which will be required to establish an abnormality of the mind is that by which a reasonable man would regards as abnormal. This test has a very wide meaning and includes the ability to exercise will power and control.

What would usually be considered to be an abnormality of the mind?

The following have been held to be an abnormality of the mind in cases of diminished responsibility:

  • Jealousy
  • Pre-menstrual tension
  • Battered woman syndrome
  • Epilepsy
  • Chronic depression

Is it enough to simply have the condition?

In order to establish an abnormality of the mind to use the defence of diminished responsibility it is not sufficient to simply have the condition. The defendant must prove that the condition was excessive when compared to that experienced by a reasonable person.

Recognised Medical Condition

Homicide Act 1957

The second condition in order to establish the defence of diminished responsibility under the original Homicide Act was that the abnormality of the mind has to be caused by an arrested or retarded development of the mind or any inherent causes or induced by disease or injury.

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For more information on:

  • What does this mean?
  • What is the case in relation to drug addicts or alcoholics?
  • What is the case in relation to prescription drugs?
  • Coroners and Justice Act 2009
  • Substantially impair the defendant’s mental responsibility
  • Homicide Act 1957
  • Coroners and Justice Act 2009
  • Provides and explanation for the defendants conduct
  • When will this provide an explanation for the conduct?
  • Diminished Responsibility on appeal