In the context of diminished responsibility, it has consistently been interpreted that the term "substantially" requires a significant and weighty justification for downgrading the offence from murder to the lesser charge of manslaughter. It is not enough to have a reason that is only marginally more than trivial.
After an argument, the appellant violently attacked his partner with a knife at their home, inflicting 22 stab wounds with blunt impact internal injuries, which resulted in her death.
As a defence, it was raised that he had a history of mental illness that required him to receive treatment and medication as an outpatient. Two consultant forensic psychiatrists provided testimony indicating that his mental functioning was abnormal due to a medically recognized condition.
The issue was whether he was under the influence of a psychotic condition at the time of the incident, thereby meeting the criteria for the partial defence of diminished responsibility under section 2 of the Homicide Act 1957.
This case provides a valuable legal commentary on the concept of diminished responsibility in criminal law. It emphasises the requirement that the abnormal mental functioning must substantially impair the defendant's mental faculties, thereby justifying a reduction in the charge from murder to manslaughter.
This interpretation ensures that the defence is invoked only in cases where there is a significant and meaningful impact on the defendant's mental capacity, promoting a fair and balanced application of the law.
In dismissing the appeal, the Court opined that:
The renewal of the attack despite the warning presence of the children and the removal of the first knife might perhaps be some indicator of self-control and give some support to the contention that the cause was simple anger rather than distorted thinking.[54]