Homicide 

Homicide is the unlawful killing of a human being. Everything else in this area is a question of fault: the physical element is common to murder and manslaughter, and the offences are separated by the accused's state of mind, or by the category of conduct the law treats as sufficient without proof of an intention to kill.

The law is not uniform. Western Australia and Queensland apply Griffith Codes, Victoria, New South Wales and South Australia apply a Crimes Act sitting on a common law base, and the fault elements and partial defences differ. Identify the jurisdiction first.

The physical element and causation

The prosecution must prove that the accused's act or omission caused the death. Causation is rarely contentious but repays care when it is. The accused's conduct need not be the sole cause; it must be a substantial or operating cause. The eggshell skull principle applies: the accused takes the victim as they find them, so an unusual vulnerability does not break the chain.

Intervening acts — medical treatment, the victim's own conduct in escaping, a third party's intervention — break the chain only if they are so independent and potent as to render the accused's contribution insignificant. Negligent medical treatment ordinarily does not.

An omission founds liability only where the accused was under a legal duty to act: a duty arising from a relationship, from the assumption of care, or from having created the danger.

Murder

Murder requires the killing plus one of the recognised fault elements, which typically include:

• an intention to kill;
• an intention to cause grievous bodily harm;
• reckless indifference to human life — foresight of death, or in some jurisdictions of grievous bodily harm, as probable; and
• constructive (or felony) murder, where death results from conduct done in the course of committing another serious offence, without proof of any intention as to the death itself.

Constructive murder is the most distinctive category and the most jurisdictionally variable. It exists in some jurisdictions and not others, and where it exists the qualifying offences are defined.

Voluntary manslaughter: the partial defences

Where the fault element for murder is established but a partial defence applies, the verdict is manslaughter rather than murder. The partial defences vary but commonly include:

• Provocation, abolished or substantially restricted in several jurisdictions following criticism that it operated to excuse killings in domestic contexts;
• Substantial impairment or diminished responsibility, where an abnormality of mind substantially impaired the accused's capacity; and
• Excessive self-defence, where the accused believed the force necessary but the belief was unreasonable.

These reduce, they do not acquit.

Involuntary manslaughter

Where the fault element for murder is absent, two routes remain:

Unlawful and dangerous act manslaughter requires an unlawful act — a criminal offence, not merely a tort — that a reasonable person in the accused's position would have realised exposed another to an appreciable risk of serious injury. The test is objective; the accused's own appreciation of the risk is not required.

Criminal negligence manslaughter requires a breach of a duty of care falling so far short of the standard of a reasonable person, and involving such a high risk of death or grievous bodily harm, as to warrant criminal punishment. The threshold is markedly higher than civil negligence.

Constructive and unlawful act murder

Several jurisdictions retain a form of murder committed during, or immediately after, the commission of another serious offence — variously called constructive, felony or unlawful act murder. Where it applies, the fault element for murder is supplied by the fault element for the base offence, and the prosecution need not prove any intention as to death.

The provisions are confined: the base offence must carry a specified minimum penalty, and there must be a temporal and causal connection between it and the death. Because the doctrine dispenses with fault as to the death itself, it is construed strictly and is a frequent subject of appeal.

The unborn and the deceased

A homicide requires the death of a person who was born alive and had an independent existence. Harm to a foetus is dealt with by separate offences, which differ markedly between jurisdictions, and by aggravated assault provisions where the mother is the victim.

At the other end, the accused's conduct must be a cause of death — a person already dead cannot be killed. Where the accused believes the victim is already dead and disposes of a body who is in fact alive, the analysis turns on the series-of-acts principle rather than on any single act.

Other homicide offences

Beyond murder and manslaughter, most jurisdictions provide for:

• Infanticide, where a mother causes the death of her child under a specified age while the balance of her mind was disturbed by the effects of childbirth or lactation. It operates both as a distinct offence and as a partial defence to murder.
• Dangerous or culpable driving causing death, which fills the space between manslaughter and the traffic offences and does not require the high degree of negligence manslaughter demands.
• Industrial manslaughter, enacted in most jurisdictions, imposing liability on a body corporate or a senior officer for a workplace death caused by a breach of a work health and safety duty. Its fault element and attribution rules come from the work safety statute, not from the general law of homicide.

Sentencing

Murder attracts a maximum of life imprisonment in every Australian jurisdiction, and some prescribe a standard non-parole period or a mandatory life sentence for defined categories such as the murder of a police officer.

Manslaughter carries a substantially lower maximum and a very wide range, reflecting that the category spans conduct from a single unlucky push to a sustained course of gross negligence. The partial defences matter enormously in practice for that reason: reducing murder to manslaughter removes the life maximum and opens the full sentencing range.

Applying this in a problem question

1. Establish the death and the causal link, dealing with any intervening act expressly.
2. Identify the jurisdiction, because it determines the available fault elements and partial defences.
3. Work through the murder fault elements in order, and address constructive murder only if the jurisdiction recognises it.
4. If murder is made out, consider each partial defence the facts raise.
5. If it is not, take both involuntary manslaughter routes separately — they have different tests and an answer that merges them loses marks.

Self-check

• Have I identified whether a Code or the common law governs before applying any fault element?
• Have I dealt with causation rather than assuming it?
• Have I kept the partial defences as reductions, not acquittals?
• Have I applied unlawful and dangerous act and criminal negligence as separate routes?