Every crime has two parts: the actus reus (guilty act) and the mens rea (guilty mind). Half of OCR Paper 1 hinges on knowing the difference.
This article is the simplified version of one section of LawByLak Topic 1. We'll cover what actus reus actually means, why voluntariness matters, the general rule on omissions, and the six categories of duty that displace it — with the five cases that examiners reach for over and over.
The three things you need to know
- Actus reus is the physical part of a crime — your conduct, any required result, and any required circumstances. Not what was in your head.
- It has to be voluntary. A sneeze isn't a punch. A seizure isn't dangerous driving. (See Hill v Baxter.)
- Doing nothing is usually fine — but six categories of duty turn an omission into an offence. Memorise them. They're the whole topic.
What actus reus actually is
Let's start with what it actually means, because most textbooks make this harder than it needs to be. Actus reus is the external, observable part of a crime — everything outside the defendant's head. It has three components, and the marks live in your ability to name each one separately:
- Conduct — what the defendant physically did, or in some cases, failed to do.
- Result — any outcome the offence requires. Murder needs a death. Theft needs property to be taken. Criminal damage needs damage.
- Circumstance — any surrounding fact the offence requires. Murder requires the victim was "a reasonable person in being". Theft requires the property "belonged to another".
What actus reus does not include is anything happening in the defendant's mind. That's mens rea's job. Mixing them up is the most common A-Level mistake in this topic — we'll come back to it.
The voluntariness requirement
Quick reality check: an act only counts as an actus reus if it was voluntary. The defendant must have had conscious control of their body when it happened. A driver who has a stroke at the wheel. Someone in the middle of an epileptic seizure. A person stung by a swarm of bees. None of these satisfy the actus reus requirement — because the body was acting without the mind directing it.
- Facts
- The defendant drove through a halt sign and into another car. He claimed to have been in some kind of trance and had no recollection.
- Principle
- The defence requires actual loss of voluntary control. The court's famous illustration: a driver attacked by a swarm of bees, or struck by a stone, or having a sudden unforeseeable seizure, would not be acting voluntarily — their body would be moving but they would not be in control.
- Element it proves
- Actus reus must be voluntary. Without conscious control, there is no actus reus.
- Use it in an exam
- "Following Hill v Baxter, the actus reus must be a voluntary act of the defendant."
- Easy to confuse with
- Bratty v AG of NI — very similar principle but in the context of the defence of automatism. Hill v Baxter is the actus reus foundation; Bratty is the defence framework.
There's a twist though: even where an act is involuntary at the moment it happens, prior fault can still bring liability home. A driver who falls asleep at the wheel after ignoring warning signs of fatigue doesn't escape conviction just because the actual crash happened while they were unconscious — the fault was earlier, when they decided to keep driving.
Acts versus omissions: the general rule
This is where most students get tripped up — and where the marks are.
English criminal law, as a general rule, punishes acts — not failures to act. If you walk past a child drowning in a pond and do nothing, you commit no offence, even if rescuing the child would have cost you nothing.
The principle is sometimes called the "well-fed man" rule, and it sits uncomfortably with most students' moral intuitions. That discomfort is exactly what AO3 evaluation questions probe — whether the rule actually strikes the right balance between individual liberty and protection of the vulnerable.
But — and this is the bit you need to know cold — the rule has six recognised exceptions. In each, the law imposes a positive duty to act. Once a duty exists, a failure to act becomes the actus reus of the offence.
You walk past someone drowning. Are you criminally liable?
You're walking home and see a stranger struggling in a canal. You're a strong swimmer. You keep walking. The stranger drowns.
Tap to see the answer
No criminal liability. You owe the stranger no duty — you didn't create the danger, you have no statutory obligation, no contract, no public role, and you haven't voluntarily taken on responsibility for them. Morally questionable, legally fine.
The flip side: if the drowning person was your child, or you'd pushed them in, or you were the on-duty lifeguard — liability follows. The duty changes the answer.
The six duties to act
There are exactly six categories. Once you know them, every omissions question gets easier — because you can spot which one the examiner is testing within seconds of reading the fact-pattern.
Statutory duty
Parliament directly imposes the duty by Act. Children and Young Persons Act 1933, s.1 (child neglect). Road Traffic Act 1988, s.170 (stopping after an accident).
Contractual duty
Your contract creates a duty owed to the public — typically in a safety-critical role.
R v Pittwood (1902)Public office
Holding a position of public responsibility carries a positive duty to act when needed.
R v Dytham [1979]Special relationship
A duty exists between parent and child, or any adult who has accepted a parental role. Biology or family role creates the hook.
R v Gibbins & Proctor (1918)Voluntary assumption
You take on the care of someone vulnerable — through age, illness, or dependence. You've accepted the duty.
R v Stone & Dobinson [1977]Creating a dangerous situation
You caused the danger and became aware of it. The duty crystallises at the moment of awareness.
R v Miller [1983]Think of the six duties as a ladder of how directly you created the duty, from "the law just imposed it on you" down to "you literally caused the problem". Each rung, you're a bit more personally involved:
- 1Statute — Parliament wrote the rule
- 2Contract — you signed up to it
- 3Public office — your role demands it
- 4Special relationship — biology or family role created it
- 5Voluntary — you took it on
- 6Danger — you caused it
The cases you actually need
These five cases turn up over and over in OCR mark schemes. Learn each one with its category attached — that's the bit examiners reward.
- Facts
- The defendant was a railway-crossing gatekeeper. He left the gate open while he went to lunch. A horse and cart crossed the line and the driver was killed by an oncoming train.
- Principle
- A failure to perform a contractual duty can amount to the actus reus of a crime. He was convicted of manslaughter.
- Use it in an exam
- "Where the defendant's contract of employment requires positive action, failing to act can constitute the actus reus: R v Pittwood."
- Easy to confuse with
- R v Adomako — also a contractual duty case (an anaesthetist failing to notice a disconnected breathing tube). Pittwood is the foundational principle; Adomako applies it to gross negligence manslaughter.
- Facts
- An on-duty police officer stood by while a man was kicked to death outside a club. He did nothing to help and walked away when the violence ended.
- Principle
- A police officer holds a public office, and one of the duties of that office is to protect the public from violence. The wilful neglect of that duty was an offence in itself (misconduct in public office).
- Use it in an exam
- "Holders of public office owe a duty to act, the breach of which can amount to an offence: R v Dytham."
- Facts
- A father and his partner deliberately starved his seven-year-old daughter to death by withholding food.
- Principle
- A parent owes their child a duty of care arising out of the special relationship. So does any adult who has accepted a parental role. Both defendants were convicted of murder.
- Use it in an exam
- "A duty to act arises from special relationships such as that of parent and child: R v Gibbins & Proctor."
- Facts
- Stone's elderly sister came to live with him and his partner Dobinson. She suffered from anorexia and became bedridden. Stone and Dobinson made some attempts to call for help but did not do so effectively. The sister died.
- Principle
- By taking her in and beginning to care for her, the defendants had voluntarily assumed a duty of care towards her. They could not abandon that duty without ensuring help was sought.
- Use it in an exam
- "A duty to act can arise where the defendant has voluntarily assumed responsibility for another's care: R v Stone & Dobinson."
- Easy to confuse with
- R v Gibbins & Proctor: both involve neglect leading to death. The difference is the source of the duty — Gibbins is a special relationship by blood; Stone is a duty voluntarily assumed.
- Facts
- The defendant, a homeless man, fell asleep in a building with a lit cigarette. When he woke and saw his mattress was on fire, he simply moved to another room and went back to sleep. The building was damaged.
- Principle
- Where the defendant has accidentally set in motion a dangerous chain of events, he is under a duty to take reasonable steps to counter it. Failing to do so can be the actus reus.
- Use it in an exam
- "A defendant who creates a dangerous situation owes a duty to take reasonable steps to address it: R v Miller."
OCR mark schemes consistently reward candidates who identify which category of duty the case establishes — not just the case name. A candidate who writes "the defendant was like in Stone & Dobinson" earns less than one who writes "the defendant voluntarily assumed responsibility for the victim, as in Stone & Dobinson".
The category is the legal handle. The case is the authority for it. Mark schemes treat them as two separate marks — so make both visible.
Source: pattern noted across OCR H418/01 examiner reports, 2022–2024 cycle.Year 13 students routinely run the two together. "He intended to kill" is mens rea — not actus reus. "The victim died" is actus reus — not mens rea.
The cleanest exam structure is to deal with them in separate paragraphs: state the actus reus, prove each element, then state the mens rea, prove each element, then deal with coincidence. Examiners flag this every cycle.
How this actually appears on the exam
OCR's H418/01 paper rarely asks "what is actus reus?" directly. The questions embed it inside a longer fact-pattern — usually a homicide scenario — and expect you to identify the relevant duty type, name the case authority, and apply it to the facts.
A candidate who writes a textbook-perfect definition of R v Miller without explaining how the squatter analogy maps onto the exam's fact-pattern won't break Level 2. A candidate who correctly identifies "creation of danger", cites Miller in one line, and spends three sentences applying it to the facts will sit comfortably at Level 4.
Examiner reports from the 2022–2024 cycle repeatedly flag the same weakness: students name the cases but can't say which limb of the duty test the case establishes. The fix: memorise every case with its category attached — never as a free-floating fact.
For evaluation questions, this is the classic debate. For the rule: criminal law should punish wrongdoing, not require heroism; converting moral duties into legal ones would over-criminalise; line-drawing problems would be impossible (how good a swimmer must I be?).
Against: most other European systems impose at least a duty of "easy rescue"; the rule produces morally repugnant outcomes; the existing six-category framework is already so broad that the principled distinction is hard to defend.
A Level 4 evaluation paragraph acknowledges both sides, then commits to one — usually by reference to the proportionality of the criminal sanction.
Boom — that's actus reus
- Actus reus = the physical part of a crime: conduct, result, circumstance.
- It must be voluntary (Hill v Baxter), unless there's prior fault.
- Omissions usually don't count — unless one of the six duties applies.
- The six duties: statute, contract, public office, special relationship, voluntary assumption, creation of danger.
- The five killer cases: Pittwood, Dytham, Gibbins & Proctor, Stone & Dobinson, Miller.
- In the exam: name the duty type AND cite the case AND apply it to the facts. That's a Level 4 answer.
Criminal Liability
Walk into Paper 1 knowing exactly which duty to cite.
A fact-pattern comes up. You don't panic. In five seconds you spot the category — voluntary assumption — cite Stone & Dobinson, apply it to the facts, and move on knowing that paragraph just earned Level 4. That's what Topic 1 is for.
- Every case rated ⭐⭐⭐ by priority — so you know at a glance which cases must be in your answer
- "Say It In An Exam" boxes — the exact phrasing OCR and AQA examiners reward, ready to drop straight into your answer
- "Easy to confuse with" notes — distinguishing similar cases (e.g. Pittwood vs Adomako) so you never cite the wrong one
- Real examiner-report evidence with year + page citations — the lines that move you from Level 3 to Level 4
- Facts
- The defendant was a railway-crossing gatekeeper. He left the gate open while he went to lunch. A horse and cart crossed the line and the driver was killed by an oncoming train.
- Principle
- A failure to perform a contractual duty can amount to the actus reus of a crime. He was convicted of manslaughter.
- Use it in an exam
- "Where the defendant's contract of employment requires positive action, failing to act can constitute the actus reus: R v Pittwood."
- Easy to confuse with
- R v Adomako — also a contractual duty case (an anaesthetist failing to notice a disconnected breathing tube). Pittwood is the foundational principle; Adomako applies it to gross negligence manslaughter.