Diminished responsibility in England and Wales: the four-part test

What does diminished responsibility mean?

Diminished responsibility is a partial defence to murder. If it succeeds, the person is convicted of manslaughter instead of murder (Homicide Act 1957 s2(3)).

It applies only to someone who 'kills or is a party to the killing', so it's not available for attempted murder. The current test came in with the Coroners and Justice Act 2009, in force from October 2010. The idea itself came from Scots law (Dowds, 2012).

The four-part test

The defence must prove all four parts (s2(1) and (2)):

• An abnormality of mental functioning. This is the starting point, and they must have been suffering from it when they killed.
• A recognised medical condition. The abnormality must arise from one (s2(1)(a)).
• Substantial impairment. It substantially impaired their ability to understand the nature of their conduct, form a rational judgement or exercise self-control. One of the three is enough (s2(1)(b) and (1A)).
• An explanation. It explains what they did, which means it caused, or was a significant contributory factor in causing, their conduct (s2(1)(c) and (1B)).

A diagnosis alone isn't enough. A recognised medical condition is necessary, but not always sufficient (Dowds, 2012).

What counts as a recognised medical condition?

The phrase was meant to point experts to the international classifications, ICD and DSM, without writing them into the Act (Dowds, 2012). Being listed isn't the end of it, though. Dowds warned that some listed conditions, such as intermittent explosive disorder, may simply describe behaviour rather than explain it. The court also left open whether genuine temporary conditions, such as concussion, could qualify.

What does 'substantially' mean? Golds

'Substantially' means important or weighty, and whether the impairment was substantial is for the jury (R v Golds, 2016). You can say whether you think it was. But the jury decides that, and whether the abnormality explains the killing.

Who proves it, and who decides?

• The defence proves it, on the balance of probabilities (s2(2)).
• The jury decides whether each element is made out.
• The prosecution can answer it. If the defence raises insanity at a murder trial, the prosecution can bring evidence of diminished responsibility, and the other way round (1964 Act s6).
• Co-defendants. One party's diminished responsibility doesn't stop the killing being murder for anyone else involved (s2(4)).

Diminished responsibility and intoxication

Voluntary acute intoxication, from alcohol or any other drug, can't found the defence. That's so even though ICD lists acute intoxication as a condition (Dowds, 2012).

A recognised condition such as alcohol dependence syndrome can be. And where someone has another qualifying condition and was also drunk, the House of Lords held in Dietschmann (2003) that the jury sets the drink aside. It asks whether the condition itself substantially impaired them.

Diminished responsibility vs loss of control

The triggers are fear of serious violence, or things said or done that were extremely grave and gave a justifiable sense of being seriously wronged. Sexual infidelity doesn't count, and a considered desire for revenge rules the defence out (ss54(4), 55). Loss of control replaced provocation, abolished in October 2010 (s56).

A condition that only lowers someone's general tolerance or self-restraint is left out of the loss of control comparison (s54(3)). That's where diminished responsibility comes in.

Diminished responsibility vs insanity

Diminished responsibility is the wider test. Someone can know exactly what they're doing, and that it's wrong, and still have substantially impaired judgement or self-control. See the insanity defence.

Sentencing after a diminished responsibility verdict

Murder carries a sentence fixed by law, so a hospital order isn't available on a murder conviction. Manslaughter is different. The court can choose a hospital order, with restrictions if needed, a s45A hospital direction, or prison. Your evidence on disposal matters (Sentencing Council guideline, annex C).

Writing a report on diminished responsibility

1. Establish the diagnosis at the time of the killing, in ICD or DSM terms.
2. Describe the abnormality of mental functioning it caused then, kept separate from how they are now.
3. Take each of the three abilities in turn, and give your evidence on each.
4. Explain how the abnormality relates to what they did: did it cause it, or contribute significantly?
5. Deal with intoxication separately, and say what the picture would be without it.
6. Give your view on whether the impairment was substantial if you're asked, and leave the decision to the jury.

See psychiatric reports for court for your duties as an expert.

A worked example

Schizophrenia is a recognised medical condition. Her persecutory delusion may well have impaired her ability to form a rational judgement, and you'd explain how it drove the killing. Set the alcohol aside and ask whether the psychosis alone substantially impaired her. Insanity may also be argued, but only if she knew neither that the act was illegal nor that it was wrong by ordinary standards. The jury decides.

Diminished responsibility in Scotland

The Homicide Act's rules don't extend to Scotland (s13(1)). Scotland has its own version of diminished responsibility, set out in statute by the Criminal Justice and Licensing (Scotland) Act 2010 (Dowds, 2012).