Homicide offences - Involuntary manslaughter (unlawful act a...

Learning Outcomes

This article outlines involuntary manslaughter—unlawful act and gross negligence—clarifying core elements, risk thresholds, omissions, causation, and exam‑focused decision‑making for SQE1, including:

• Elements and proof structure of unlawful act manslaughter and gross negligence manslaughter, with emphasis on identifying the correct offence on given facts and setting out the elements in a logical order in answers
• Distinction between a “dangerous” unlawful act (risk of some harm) and a “serious and obvious risk of death” for gross negligence, and how to articulate these thresholds using the appropriate objective tests
• Role of omissions in unlawful act manslaughter versus gross negligence manslaughter, enabling precise recognition of when liability should instead be structured as a breach‑of‑duty offence
• Causation issues in both offences, including escape cases, medical treatment, drug self‑administration, and situations involving a continuing duty arising from the creation of danger
• Objective tests for dangerousness and obvious risk, including the knowledge attributed to the sober and reasonable person and how exam questions often mislead on what the defendant must actually foresee
• Base offence (actus reus and mens rea fully established) in unlawful act manslaughter, and civil duty, breach, and grossness in gross negligence manslaughter, highlighting which elements are for the judge and which are for the jury
• Decision‑maker for each element (judge or jury), the sequence of issues to address in problem questions, and common analytical traps that lead candidates to misapply the risk tests or confuse the two offences

SQE1 Syllabus

For SQE1, you are required to understand involuntary manslaughter (unlawful act and gross negligence), with a focus on the following syllabus points:

• the elements of unlawful act manslaughter (constructive manslaughter)
• the elements of gross negligence manslaughter
• the distinction between unlawful act and gross negligence manslaughter
• the requirements for dangerousness, duty of care, breach, causation, and grossness
• how the courts assess risk of death and the role of omissions
• applying these rules to practical scenarios and avoiding common errors

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which of the following is required for unlawful act manslaughter?
   1. a civil wrong
   2. a dangerous and unlawful act
   3. an omission
   4. proof of intention to kill
2. Which of the following is NOT an element of gross negligence manslaughter?
   1. a duty of care owed to the victim
   2. a breach of that duty
   3. intention to cause serious harm
   4. a risk of death that was obvious

3. True or false? For unlawful act manslaughter, the defendant must foresee the risk of death.

4. In gross negligence manslaughter, who decides whether the breach was "gross"?

Introduction

Involuntary manslaughter covers unlawful killings where the defendant did not intend to kill or cause grievous bodily harm. For SQE1, the two principal forms are unlawful act manslaughter (constructive manslaughter) and gross negligence manslaughter. Although both are “involuntary”, their legal architecture is different: unlawful act manslaughter is built from a separate criminal act that is dangerous and causes death; gross negligence manslaughter mirrors civil negligence principles but demands a gross breach creating a serious and obvious risk of death. Understanding these frameworks, the objective tests used by the courts, and the typical causation pitfalls is critical.

Unlawful Act Manslaughter

Unlawful act manslaughter occurs when a person intentionally does an unlawful and dangerous act that causes death, even if they did not intend harm. The prosecution must prove four elements:

1. The defendant did a positive act (not an omission).
2. The act was a criminal offence (not merely a civil wrong).
3. The act was objectively dangerous.
4. The act caused the victim’s death.

Key Term: unlawful act manslaughter
A form of involuntary manslaughter where death results from a defendant’s intentional, unlawful, and dangerous act.

Key Term: dangerous act
An act that all sober and reasonable people would recognise as subjecting another to the risk of some physical harm.

The Unlawful Act

The act must be a crime requiring a positive action. Omissions do not suffice: if the conduct is an omission, unlawful act manslaughter is not available and the analysis turns to gross negligence manslaughter. The principal offence may be any crime with mens rea of intention or recklessness (e.g., assault or battery, robbery, burglary, criminal damage, arson), but not a mere civil wrong and not an offence satisfied only by negligence or strict liability. It is not enough that the act is lawful per se but carelessly performed; a lawful act done negligently cannot serve as the “unlawful act” basis.

The base offence must be proved in full: both actus reus and mens rea must be established and no defence must apply. If the base offence fails (for example, no battery because the victim did not apprehend force or there was no intention or recklessness), unlawful act manslaughter collapses.

Two clarifications help:

• The unlawful act need not be aimed at the eventual victim, and need not be a “person” offence. Property offences (e.g., arson) can suffice, provided the act is dangerous to a person.
• The defendant’s motive is irrelevant; what matters is that they deliberately performed the criminal act.

Dangerousness

Dangerousness is judged objectively. The classic formulation asks whether all sober and reasonable people would inevitably recognise that the act must subject the other person to the risk of some harm (not necessarily serious harm). Several points follow:

• The reasonable person is attributed what a bystander at the scene would glean as events unfold. The reasonable person does not make unreasonable mistakes, but will have knowledge the defendant actually had and any facts obvious at the scene (for example, that the householder is elderly and frail).
• The risk threshold is modest: risk of “some harm” suffices. There is no need that the reasonable person would foresee death or really serious harm.
• “Harm” is ordinarily physical harm. Property offences can be “dangerous” if they carry an obvious risk of physical harm to someone (e.g., arson of a dwelling).

Although the defendant’s own appreciation of danger is not required, the objective test is informed by the context apparent to the reasonable person. Thus, if the unlawful act is a burglary of an elderly and obviously frail person’s home at night, the reasonable bystander may recognise a risk of some harm even if the defendant did not.

Causation

The unlawful and dangerous act must cause death, applying ordinary principles of factual and legal causation. Where the victim acts to escape, the chain is not broken if the reaction falls within the range of reasonably foreseeable responses to the defendant’s act. Medical negligence will rarely break the chain unless it renders the original contribution insignificant. In drug cases, self‑administration by a fully informed adult typically breaks the chain between supply and death; by contrast, where the defendant creates or contributes to a life‑threatening situation and then fails to act, liability may arise (usually under gross negligence) due to a continuing duty.

Worked Example 1.1

A group of friends throw stones at passing trains as a prank. One stone breaks a window, fatally injuring a passenger. Can the thrower be convicted of unlawful act manslaughter?

Answer:
Yes. Throwing stones at a train is a criminal offence and a dangerous act; a sober and reasonable person would recognise a risk of some harm. The act caused death and the defendant’s foresight of death is unnecessary.

Exam Warning

For unlawful act manslaughter, the act must be a crime and a positive act. Omissions, even if grossly negligent, cannot be the basis for this offence.

Worked Example 1.2

A defendant pushes someone during an argument. The victim falls, hits their head, and dies. The push was intended as a minor assault. Is this unlawful act manslaughter?

Answer:
Yes. The push is a battery (a criminal offence), and pushing someone is objectively dangerous because it carries a risk of some harm. The act caused death.

Additional points frequently tested

• Mens rea: the defendant need only have the mens rea for the base offence. They need not foresee harm, serious harm, or death.
• Base offence defences: if the defendant can rely on a defence to the base offence (e.g., self‑defence defeats the battery), unlawful act manslaughter fails.
• Drug supply: where a fully informed adult self‑administers, the free and voluntary injection ordinarily breaks the chain. If the defendant administers the drug or creates a life‑threatening state of affairs and then fails to summon help, liability may arise—usually as gross negligence—not as unlawful act manslaughter.

Gross Negligence Manslaughter

Gross negligence manslaughter arises when a person owes a duty of care to the victim, breaches that duty in a grossly negligent way, and causes death. The prosecution must prove:

1. The defendant owed the victim a duty of care.
2. The defendant breached that duty.
3. The breach caused the death.
4. The breach involved a serious and obvious risk of death.
5. The breach was grossly negligent.

Key Term: gross negligence manslaughter
A form of involuntary manslaughter where death results from a defendant’s gross breach of a duty of care.

Key Term: duty of care
A legal obligation to take reasonable care to avoid acts or omissions which could foreseeably injure another.

Key Term: gross negligence
Conduct so far below the standard expected of a reasonable person that it amounts to a crime deserving punishment.

Duty of Care

The question whether a duty of care exists is approached using civil negligence principles and is in the first instance a matter for the judge. Duties are familiar in medical, professional, landlord/tenant and driver/road‑user contexts, and can also arise from assuming responsibility or creating a dangerous situation. Where the defendant creates or contributes to a life‑threatening state of affairs, a duty to take reasonable steps to save life may arise. In assessing criminal liability, civil illegality principles do not negate the existence of a duty: a duty can be owed even to a person engaged with the defendant in unlawful activity.

Omissions play a central role: gross negligence manslaughter can be committed by failing to act where a duty exists (e.g., failure to call an ambulance for someone overdosing after the defendant supplied drugs and realised the risk).

Breach and Risk

Breach is established by showing that the defendant’s conduct fell below the standard of the reasonable person in that position (with any special skills attributed to that notional comparator). In addition, the breach must carry a serious and obvious risk of death—obvious in the sense of present, clear and apparent at the time of breach, not something that only emerges on further investigation. The test is objective: would a reasonably competent practitioner (or person in the defendant’s position) have appreciated the serious and obvious risk of death at the material time?

• “Serious and obvious risk of death” is a higher threshold than “risk of some harm.” It is not enough that there was a risk of injury or even serious injury; the risk in question must be of death.
• The focus is on the state of knowledge at the time of the breach; hindsight is avoided.

Causation (Gross Negligence Manslaughter)

Ordinary rules of factual and legal causation apply. The breach must make a more than minimal, operating and substantial contribution to the death. Medical negligence will seldom sever the chain unless it renders the defendant’s contribution insignificant. Omissions by third parties rarely break the chain; the original breach commonly remains an effective cause.

Grossness

Finally, the breach must be so bad as to amount to a criminal act or omission. This is a jury question: having regard to the risk of death involved, was the defendant’s conduct so reprehensible as to merit criminal sanction? Expert evidence may assist on standards but the ultimate evaluation of “grossness” is for the jury.

Factors which may guide, but not replace, the jury’s judgment include: how far short of the expected standard the conduct fell; the gravity and obviousness of the risk of death; the nature of the defendant’s role and responsibilities; and whether the conduct showed a disregard for life and safety.

Worked Example 1.3

A landlord ignores repeated complaints about a faulty gas boiler. The boiler leaks carbon monoxide, killing a tenant. Is this gross negligence manslaughter?

Answer:
Yes. The landlord owed a duty of care, breached it by failing to address the hazard, the breach caused death, the risk of death (carbon monoxide) was serious and obvious to a reasonable landlord at the time, and the jury could find the breach gross.

Worked Example 1.4

D supplies heroin to V, watches V self‑inject and recognises V is deteriorating. D decides not to call an ambulance to avoid trouble. V dies. Is D liable for unlawful act manslaughter or gross negligence manslaughter?

Answer:
On these facts gross negligence manslaughter is more likely. V’s free and voluntary self‑administration usually breaks the chain for unlawful act manslaughter. But D created or contributed to a life‑threatening situation and, realising the danger, omitted to act. A duty to summon help arose; breach, causation, serious and obvious risk of death, and grossness may all be satisfied.

Worked Example 1.5

A trainee optometrist fails to conduct essential checks that would have revealed a condition placing a patient at serious risk of fatal collapse. The patient later dies. Is the risk requirement met?

Answer:
The question is whether, at the time of breach, a reasonably competent practitioner would have identified a serious and obvious risk of death. If the missing checks would have made that risk apparent then the requirement may be satisfied; if the risk of death was not then obvious (only injury or a risk apparent only after further investigation), the element may fail.

Revision Tip

For gross negligence manslaughter, always check for a duty of care, a breach, causation, an obvious risk of death apparent at the time of breach, and whether the breach is gross. Remember that unlawful act manslaughter cannot be based on an omission; where the facts concern a failure to act in the face of a duty, gross negligence manslaughter is the correct analysis.

Comparing the Offences

Key Point Checklist

This article has covered the following key knowledge points:

• Unlawful act manslaughter requires a positive, criminal, and dangerous act causing death.
• The act must be objectively dangerous; the defendant’s awareness is irrelevant.
• The base offence must be proved in full; if a defence to it succeeds, unlawful act manslaughter fails.
• Unlawful act manslaughter cannot be founded on an omission or on negligence/strict liability alone.
• Gross negligence manslaughter requires a duty of care, breach, causation, a serious and obvious risk of death judged at the time of breach, and grossness.
• The jury decides whether negligence is “gross” in gross negligence manslaughter.
• Omissions can found gross negligence manslaughter but not unlawful act manslaughter.
• In drug cases, a fully informed adult’s self‑administration ordinarily breaks the chain for unlawful act manslaughter; a duty to act may nonetheless arise for gross negligence manslaughter.
• Distinguish risk thresholds carefully: “some harm” (unlawful act) versus “serious and obvious risk of death” (gross negligence).

Key Terms and Concepts

• unlawful act manslaughter
• dangerous act
• gross negligence manslaughter
• duty of care
• gross negligence