Diminished responsibility is a partial defence to murder which if proven can reduce the conviction to manslaughter. This allows the court a greater breadth of sentencing options.
In the late nineteenth and early twentieth century the mandatory sentence for murder was capital punishment. This was a major factor in the conception of diminished responsibility legislation.
The partial defence meant that the death penalty might be avoided in homicide cases where the accused was mentally disordered, but did not meet the threshold for insanity.
The Infanticide Act 1922 was an example from the same time period which reflected a will from Parliament to avoid harsh treatment for mentally disordered offenders.
Diminished responsibility was established in Scottish case law long before proposals were made to include the law in England and Wales. In 1867 a murder charge was downgraded in the case of Dingwall due to a ‘weakness of mind’ in the accused.
By the early twentieth century the phrase ‘diminished responsibility’ was being used regularly in Scottish courts to reduce murder convictions to manslaughter.
The Homicide Act 1957 set out the criteria for diminished responsibility in England and Wales. Several years later the Murder (Abolition of Death Penalty) Act 1965 replaced capital punishment with a mandatory sentence of life imprisonment.
The criteria for diminished responsibility were amended by the Coroners and Justice Act 2009.