On Voluntary Manslaughter (Part 2).

This is part two of my analysis of voluntary manslaughter. You can read part one here.

I have also previously covered the equation for criminal liability, and you can read about it here.

The test for diminished responsibility attempts to strike a balance between providing justice for the defendant’s circumstances while still recognizing the seriousness of the offence. After all, a human being was unlawfully killed –this is no minor thing.

The test for the mistress possibility is exactly the same as a general equation for criminal liability:


As previously discussed, the AR of all Homicide is the unlawful killing of a human being. The MR of murder is to have the intention to kill or cause serious injury.

The D element it’s for diminished responsibility. This can be an abnormality of mental functioning which arises from a recognised medical condition that substantially impaired the defendant’s ability to understand and exercise rational judgment at the time of the killing. Diminish responsibility can also be due to a lack of self-control defence based on what the victim said or did.

I think, at this point, it is worth quoting directly from section 2 of the Homicide Act of 1957:

(1) A person (‘D’) who kills or is a party to the killing of another is not to be convicted of murder if D was suffering from an abnormality of mental functioning which –

arose from a recognised medical condition,

substantially impaired D’s ability to do one or more of the things mentioned in subsection (1A), and

provides an explanation for D’s acts and omissions in doing or being a party to the killing.

(1A) Those things are –

a. to understand the nature of D’s conduct; b. to form a rational judgment;

c. to exercise self-control.

(1B) For the purposes of subsection (1)(c), an abnormality of mental functioning provides an explanation for D’s conduct if it causes, or is a significant contributory factor in causing, D to carry out that conduct.

(2) On a charge of murder, it shall be for the defence to prove that the person charged is by virtue of this section not liable to be convicted of murder.

So to summarize, a defendant who kills will not be convicted of murder if the following requirements are met:

  1. The defendant is suffering from an abnormality of mental functioning.
  2. This arises from a recognised medical condition.
  3. The defendant must have a substantially impaired ability:
  4. a. to understand the nature of their conduct, b. to form a rational judgement, c. to exercise self-control.

The abnormality of mental functioning must explain for (i.e. be a significant contributory factor to) the defendant’s conduct.

Let’s now cover each one of these in detail.

An abnormality of mental functioning.

To pass the first part of the diminished responsibility test, the defendant must have an abnormality of mental functioning. But what does this mean? It’s up to each court to interpret this for each case. In R v Byrne, Lord Parker CJ provided a useful definition: “a state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal.”

This is a broad term. It means that a person with a normal functioning mind would consider another’s mind to be abnormally functioning. It is an objective test. The jury must think like a reasonable person, not the specific defendant in the case. It does not matter if the defendant thought their actions were reasonable or normal.

It’s easy to criticize this idea. Does it assume everyone in a certain country is the same? That’s not true. In fact, many countries are very diverse, composed of many individuals with different ideas of what it means to be reasonable. This problem was highlighted in the past when the term “Reasonable man” was used and referred to as the “man on the Clapham Omnibus”.

Today, courts must recognize that the “reasonable person” may not be a male, middle-class Londoner. Juries hear medical evidence from professionals but are not obligated to follow it. Ultimately, it is up to the jury to decide if the defence of diminished responsibility succeeds or fails.

Recognized Medical Condition.

The statutory test requires you to have a degree of mental impairment caused by a recognized medical condition. Usually, the medical condition is mental, but it doesn’t have to be. Physical conditions such as epilepsy can also cause an abnormality of mental functioning.

This is not straightforward. For example, consider someone intoxicated due to alcohol consumption, especially if they are an alcoholic. Should this be recognized as a medical condition, or should they be less accountable for actions taken while under the influence of alcohol?

The term “substantially impaired ability” implies that the defendant cannot comprehend the nature of the contact, make rational decisions, or control themselves.

Mental dysfunction must contribute significantly to a defendant killing another human being, but it does not have to be the only cause of their conduct.

Let’s discuss the burden and standard of proof.

In part one, we discussed that any partial defence to murder, such as diminished responsibility, can only be considered after the Actus Reus and Mens Rea of murder have been established.

The prosecution must prove beyond reasonable doubt that the defendant is guilty. This means that the jury must be certain of the defendant’s guilt.

The burden of proof shifts to the defendant when it comes to the defence of diminished responsibility.

This is because the defence relates to the defendant’s internal mental condition, which is hard for the prosecution to prove without the defendant’s cooperation. The defendant only needs to prove diminished responsibility on the balance of probabilities, which is the standard used in civil cases.

This means they must show that it is more likely than not that they are entitled to the defense, not that they must prove it beyond reasonable doubt.

Domestic violence is a serious issue. It often involves killings between family members or between a boyfriend and girlfriend. The most common cause of such killings is usually a man’s jealousy or anger over a love triangle.

Men can be victims of domestic violence too. Not all relationships are between a man and a woman. Where do you stand?

Many campaigners and policymakers agree that criminal law is insufficient to tackle domestic violence and partner homicides. These issues are more complex than typical crimes. To address them, initiatives like the Domestic Homicide Review (DHR) have been developed.

In England, the law requires local councils to conduct a Domestic Homicide Review (DHR) after an adult dies from violence, abuse, or neglect by a relative, an intimate partner, or a person living in the same household.

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