24.4 General Defences
Key Takeaways
- Voluntary intoxication may prevent specific intent (murder, s.18, attempt) if the defendant did not form that intent; it is not a defence to basic-intent offences such as assault, battery, s.47 and s.20.
- Involuntary intoxication can negate mens rea even on a basic-intent offence, but if the defendant still formed the required fault, the intoxication does not excuse.
- Self-defence and defence of another are complete defences: the defendant is judged on the facts as honestly believed, and the force must be reasonable in those believed circumstances.
- A mistaken belief attributable to voluntary intoxication cannot be relied on for self-defence under the Criminal Justice and Immigration Act 2008, s.76(5).
- In a householder case, force is not reasonable if it is grossly disproportionate; force that is merely disproportionate can still be reasonable.
24.4 General Defences
Quick Answer: FLK2 names two general defences for these specified offences: intoxication, and self-defence / defence of another. Voluntary drink or drugs may block specific intent if the intent was never formed, but they do not excuse basic-intent crimes. Self-defence is a complete defence if D honestly believed it was necessary to use force and the force was reasonable in those believed circumstances. Independent OpenExamPrep study keeps insanity, duress and necessity off this list because they are not the FLK2 general defences.
Where general defences sit in the analysis
Do the offence ingredients first. A defence does not arise until there is something to defend. Partial defences (loss of control, diminished responsibility) apply only to murder and were covered in section 24.3. The two general defences on the SRA list can apply across the specified person-offences, with the important limit that intoxication behaves differently according to the mens rea of the crime charged.
Intoxication
Intoxication is not a free-standing excuse. It is a rule about whether the Crown can prove mens rea.
Voluntary intoxication (D chose to drink or take drugs, including Dutch courage where D drinks to steel himself for a crime already planned):
- If the offence is one of specific intent — intention is the only fault element — evidence of intoxication may show that D did not form that intent. Murder, s.18, theft (next chapter), and attempt are the usual specific-intent examples on this syllabus.
- If the offence is one of basic intent — it can be committed by recklessness — voluntary intoxication is no defence. Becoming drunk is treated as the culpable substitute for foresight. Assault, battery, s.47, s.20, and unlawful act manslaughter sit here.
| Offence | Intent class | Voluntary intoxication |
|---|---|---|
| Murder | Specific | May prevent intent to kill or cause GBH; a basic-intent homicide may remain |
| s.18 | Specific | May prevent the intent to cause GBH or to resist arrest |
| Attempt | Specific | May prevent the intent to commit the full offence |
| s.20 / s.47 / assault / battery | Basic | No defence |
| Unlawful act manslaughter | Basic | No defence |
| Gross negligence manslaughter | Not a specific-intent crime | Drink does not convert a gross breach into innocence |
If D is charged with s.18 and was so drunk that D formed no intent to cause GBH, s.18 fails. The same facts will often still found s.20 if D applied force and caused a wound or GBH, because s.20 is basic intent. If V died and murder intent is missing because of drink, consider unlawful act manslaughter, not an acquittal.
Dutch courage: D decides to kill, then drinks to carry it out. The earlier intent is not wiped by the later drink.
Involuntary intoxication (drink spiked; D did not know they were taking an intoxicant; unexpected reaction to a non-dangerous prescribed drug taken as directed):
- If D did not form the mens rea, D is not guilty even of a basic-intent offence.
- If D did form the mens rea — D still intended the punch — involuntary intoxication does not excuse. A disinhibited intent is still an intent.
Take care with insulin and similar cases: if D knows that failing to eat after a dose can cause a violent episode and D runs that risk, the situation is treated as culpable, not as a pure involuntary state.
Self-defence and defence of another
These are complete defences. If they succeed, D is not guilty. They are not a halfway house that reduces murder to manslaughter. Excessive force means the defence fails in full (though loss of control may still be run on overlapping facts).
The sources you must be able to apply together are the common law of self-defence and defence of others, the Criminal Law Act 1967, s.3 (reasonable force to prevent crime or to effect a lawful arrest), and the Criminal Justice and Immigration Act 2008, s.76, which restates how the reasonableness of force is judged.
Stage 1 — the trigger (subjective). Did D honestly believe that it was necessary to use force to defend themselves or another, or to prevent crime? D is judged on the facts as D believed them to be, even if D was mistaken, and even if the mistake was unreasonable — unless the mistake was attributable to voluntary intoxication (s.76(5)). A sober defendant who honestly but stupidly thinks a stranger is about to stab them is judged as if the stab were real. A drunk defendant who thinks the same because of the drink cannot rely on that mistake.
Stage 2 — the response (objective, on the believed facts). Was the force reasonable in the circumstances as D believed them? The jury may allow for the heat of the moment: D cannot be expected to weigh force to a nicety. Evidence that D did only what D instinctively thought necessary is strong evidence that the force was reasonable. There is no duty to retreat, though an opportunity to withdraw without safety cost is relevant. Pre-emptive force can be reasonable if D genuinely believed an attack was imminent.
| Question | Test | Intoxication overlay |
|---|---|---|
| Did D believe force was necessary? | Honest belief, even if mistaken and unreasonable | No reliance on a mistake caused by voluntary drink or drugs |
| Was the force reasonable? | Objective, on the believed facts; not a nicety | Drink does not make unreasonable force reasonable |
Householder cases (s.76(5A)). Where D is in a dwelling that is D's home (or a place D is not a trespasser) and V is a trespasser, the force is not reasonable if it is grossly disproportionate. Force that is merely disproportionate may still be reasonable. That is a deliberate difference from the ordinary street fight, where disproportionate force is not reasonable. It is not a licence to torture an intruder. Shooting a fleeing, unarmed teenager in the back will still fail; wrestling an intruder to the floor in the dark may pass even if, with hindsight, less force would have done.
Defence of another uses the same two stages. A passer-by who honestly believes a stranger is being attacked may use reasonable force to protect that stranger. If the stranger was in fact a plain-clothes officer arresting someone, the passer-by's honest mistake (if sober) is still the factual basis for stage 1.
s.3 force to prevent crime covers similar ground and is useful when D is not personally under attack (restraining a person who is about to glass someone across the room).
Combining defences with the person-offences
- Self-defence that succeeds makes the force lawful. Assault, battery, s.47, s.20, s.18 and murder all fail at the unlawfulness / actus reus stage.
- Self-defence that fails because the force was excessive leaves the offence intact. On a murder charge, look next at loss of control (fear of serious violence can overlap with a self-defence story) or diminished responsibility. Do not tell the client that excessive self-defence automatically reduces murder to manslaughter — it does not.
- Intoxication plus self-defence: remember s.76(5). The drunk client who imagined an attack cannot use that imagination as the believed facts.
- Intoxication plus s.18: first ask whether D formed the intent to cause GBH. If not, s.18 drops; then ask whether a basic-intent offence remains; then ask whether any sober, honest belief in the need for force is still available on the facts that do not depend on the drink.
Police-station advice in one paragraph
Identify the charge. If it is specific intent, take a careful account of how much D had drunk and what D claims they thought they were doing. If it is basic intent, do not promise that drink will help. If D says they were defending themselves or a partner, lock down the honest belief, whether any mistake came from drink, what force was used, whether the case is a householder case, and whether a considered revenge narrative will be put against them. Then apply the ingredients. That is functioning legal knowledge, not a speech about moral blame.
Official starting points: the SRA SQE1 FLK2 Assessment Specification (general defences: intoxication; self-defence / defence of another), the Criminal Justice and Immigration Act 2008, s.76, and the Criminal Law Act 1967, s.3.
A man drinks a bottle of vodka and then attacks a stranger with a broken bottle, causing a wound that amounts to grievous bodily harm. He was so intoxicated that he formed no intent to cause grievous bodily harm. His drinking was voluntary. He is charged with s.18. Which statement best describes the effect of intoxication?
A sober man sees a woman running towards him waving her arms. He honestly believes she is about to stab him. In fact she is trying to warn him about falling masonry. He pushes her away with reasonable force. She is not injured. He is charged with battery. Which statement best explains self-defence?
A householder finds an intruder in the hallway at night. In the dark the householder strikes the intruder several times with a torch and holds him until the police arrive. The force is more than was strictly necessary but is not grossly disproportionate. The intruder suffers bruising amounting to actual bodily harm. Which statement best reflects the householder rule?
A woman voluntarily takes a large quantity of illegal stimulants. She then imagines that a bus passenger is reaching for a gun and she strikes the passenger. A sober person would not have believed an attack was about to happen. She wishes to run self-defence to a battery charge. Which statement is correct?