Welcome to Necessity Defences: When Breaking the Law is Justified or Excused
Imagine being backed into a dark alleyway by an attacker, or having someone hold a gun to your head demanding that you drive a getaway car. In situations of extreme pressure, peril, or danger, people sometimes commit acts that would normally be criminal offences. This is where necessity defences come in.
In English criminal law, necessity defences recognise that human beings cannot always be expected to follow the letter of the law when faced with grave threats to life or limb. In this chapter, we will break down the three central defences under this umbrella for AQA A-Level Criminal Law (Paper 1):
1. Self-defence and prevention of crime
2. Duress by threats
3. Duress of circumstances
Don't worry if these sound similar at first! While they share the underlying theme of reacting to a crisis, the rules governing each one are distinct, logical, and easy to master once you break them down step by step.
Quick Reminder: All three of these are general defences and complete defences. If successfully argued, the defendant is found not guilty and receives a complete acquittal.
---1. Self-Defence and Prevention of Crime
Self-defence is a justificatory defence. This means the law agrees that the defendant did the right thing under the circumstances. The law permits a person to use reasonable force to protect themselves, protect someone else, protect their property, or prevent a crime.
The Two-Part Test for Self-Defence
To decide whether a defendant can successfully plead self-defence, courts ask two essential questions:
Part 1: Was the use of force necessary? (The Subjective Element)
Part 2: Was the degree of force used reasonable? (The Objective Element)
Part 1: Was Force Necessary? (Subjective)
The first question looks into the defendant's mind at the exact moment they acted:
• Honest belief: Did the defendant genuinely and honestly believe that force was necessary? The law judges the situation through the defendant's eyes, based on the facts as the defendant believed them to be.
• Mistake of fact: If the defendant made an honest mistake about the threat (for example, believing a plastic replica gun was real), they are judged according to that mistaken belief.
• The Intoxication Exception: An honest mistake cannot be relied upon if it arose because the defendant was voluntarily intoxicated by alcohol or dangerous drugs. The law does not let someone get drunk, misjudge a harmless situation, attack someone, and then claim self-defence!
Can you strike first? (Pre-emptive strikes): Yes. A person does not have to wait to be hit before defending themselves. If an attack is imminent, the law allows a pre-emptive strike to ward off danger.
Is there a duty to retreat? No. While demonstrating an unwillingness to fight can be evidence that a person was acting reasonably, there is no strict legal requirement to run away before defending yourself.
Part 2: Was the Force Reasonable? (Objective)
Once it is decided that force was necessary, the second question asks whether the amount of force was proportionate to the threat:
• Proportionality: The force used must not be excessive or disproportionate. If someone punches you, hitting back to stop them may be reasonable; pulling out a lethal weapon and stabbing them repeatedly is grossly disproportionate.
• Heat of the moment: The law recognises that a person defending themselves in an emergency cannot weigh to a nicety the exact measure of their defensive action. An honest and instinctive reaction is strong evidence that only reasonable force was used.
• The "Householder" rule: When someone is defending themselves against an intruder inside their own home, the law gives them wider latitude. In householder cases, the force used is considered reasonable unless it was grossly disproportionate.
Key Takeaway for Self-Defence
Self-defence formula: Did the defendant honestly believe force was needed? (Subjective) \(+\) Was the force proportionate in the circumstances as they saw them? (Objective) \(\implies\) Full Acquittal.
---2. Duress by Threats
Unlike self-defence, duress is an excusatory defence. The law recognises that the defendant committed a wrong, but excuses them because their will was completely overborne by serious threats from another human being.
Analogy: Imagine a criminal pointing a gun at a cashier and saying: "Steal that cash drawer right now and give it to me, or I will shoot you dead." The cashier has stolen money, but they only did so because their free will was destroyed by terror.
The Core Requirements of Duress by Threats
A. The Nature of the Threat
The threat must be extremely severe:
• It must be a threat of death or serious personal injury (grievous bodily harm).
• Threats to expose secrets, damage property, or inflict minor pain are strictly not enough.
• The threat must be directed at the defendant, a member of their immediate family, or someone for whose safety the defendant would reasonably feel responsible.
B. The Two-Stage Test
To determine if the defence of duress succeeds, courts apply a two-stage test:
1. The Subjective Stage: Did the defendant reasonably believe the threat of death or serious injury would be carried out immediately, or almost immediately, if they did not commit the offence?
2. The Objective Stage: Would a sober person of reasonable firmness, sharing the defendant's relevant characteristics, have responded to the threat in the same way?
Relevant characteristics: When looking at the "person of reasonable firmness", the law takes into account age, sex, pregnancy, serious physical disability, and recognised mental psychiatric conditions that affect firmness. However, characteristics like low self-esteem, timidity, or voluntary intoxication are strictly excluded!
C. Imminence and Avenue of Escape
The threat must be hanging over the defendant at the time the crime is committed:
• No safe avenue of escape: If the defendant had an opportunity to escape, seek police protection, or neutralise the threat without committing the crime, the defence fails.
• Nominated crime: For duress by threats, the coercer must generally nominate the specific crime that the defendant is ordered to carry out.
D. Self-Induced Duress (Voluntary Association)
If the defendant voluntarily joins a violent criminal gang, drug-dealing syndicate, or terrorist organisation, they cannot later rely on duress if members of that group threaten them. By freely joining a violent group, the defendant is held to have voluntarily exposed themselves to the risk of coercion.
E. Excluded Offences
The law draws a hard moral line: duress is NEVER a defence to murder or attempted murder. The common law principle holds that an innocent person must choose to sacrifice their own life rather than take the life of another innocent person.
Key Takeaway for Duress by Threats
Duress excuses a defendant who commits a crime under threat of death or serious injury, where a person of reasonable firmness would have acted the same way, with no safe escape, provided the crime is not murder or attempted murder.
---3. Duress of Circumstances
What happens if the deadly peril does not come from a person giving orders, but from an emergency situation or hostile external circumstances?
This is called duress of circumstances. Here, the pressure to commit an offence arises from an objective danger or threatening environment rather than a person commanding: "Do this specific crime or else!"
Everyday Example of Duress of Circumstances
Imagine a driver who is legally disqualified from driving. While sitting in the passenger seat of a car, a gang of armed attackers surrounds the vehicle, smashing the windows and threatening to kill everyone inside. The driver climbs into the driving seat and speeds away to save lives. He has committed the offence of driving while disqualified, but he did so solely to escape lethal danger.
The Test for Duress of Circumstances
The legal test is virtually identical to duress by threats:
1. Imminent threat: Did the defendant honestly and reasonably believe that there was an imminent threat of death or serious injury arising from the circumstances?
2. Objective firmness: Would a sober person of reasonable firmness, sharing the defendant's characteristics, have reacted in the same way to avoid the threat?
3. Proportionality: Was the criminal act proportionate to the danger faced?
4. Duration: Did the defendant cease committing the offence as soon as the danger had passed? (You cannot keep driving for hours after escaping the attackers!).
Limitations on Duress of Circumstances
Just like duress by threats, duress of circumstances is strictly not available for murder or attempted murder. It is most commonly seen in road traffic offences or public order matters where someone acts out of immediate desperation to preserve life.
Key Takeaway for Duress of Circumstances
Duress of circumstances applies when extreme external conditions force a person to commit an offence to avoid death or serious injury. The test mirrors duress by threats: an honest/reasonable belief in peril \(+\) a sober person of reasonable firmness would have broken the law in the same way.
---Summary Comparison: The Three Defences at a Glance
• Self-Defence / Prevention of Crime:
- Trigger: Unlawful attack, threat of attack, or crime in progress.
- Core Test: Force was honestly believed necessary (subjective) and the degree of force was reasonable/proportionate (objective).
- Available for Murder? Yes (if reasonable and necessary, it is a complete defence to murder).
- Result: Full acquittal.
• Duress by Threats:
- Trigger: Human threat of death or serious injury compelling a specific crime.
- Core Test: Defendant reasonably believed threat would be carried out (subjective) and a sober person of reasonable firmness would have complied (objective).
- Available for Murder? No (never available for murder or attempted murder).
- Result: Full acquittal.
• Duress of Circumstances:
- Trigger: External emergency or dangerous situation compelling a criminal response.
- Core Test: Defendant reasonably perceived imminent death or serious injury (subjective) and a sober person of reasonable firmness would have acted identically (objective).
- Available for Murder? No (never available for murder or attempted murder).
- Result: Full acquittal.
Common Mistakes to Avoid in Paper 1
• Confusing Self-Defence with Duress on Murder charges: Remember that self-defence CAN defend against a murder charge (killing an attacker in necessary self-defence using reasonable force is completely lawful). Duress can NEVER defend against a murder or attempted murder charge.
• Forgetting Voluntary Intoxication rules: If a defendant mistakenly believes they are under attack because they are drunk, their self-defence claim fails. Similarly, being drunk does not lower the standard of the "sober person of reasonable firmness" in duress.
• Ignoring Safe Avenues of Escape: In duress, always check if the defendant could have gone to the police, locked themselves in a safe place, or walked away. If a safe avenue existed, duress is destroyed.
• Missing Self-Induced Duress: If the problem scenario mentions that the defendant willingly joined a criminal gang known for violence, evaluate whether they lost their right to claim duress by walking into the danger voluntarily.
Step-by-Step Problem Solving Framework for Exam Scenarios
When an exam question presents a scenario involving danger, threats, or emergencies, follow this step-by-step structure:
Step 1: Identify the correct defence.
Is the defendant repelling an attack/preventing a crime (Self-Defence)? Are they obeying a threat made by a person (Duress by Threats)? Or are they escaping an emergency situation (Duress of Circumstances)?
Step 2: Check offence eligibility.
Is the charge murder or attempted murder? If yes, duress cannot apply at all, but self-defence can.
Step 3: Apply the subjective element.
What was the defendant's honest belief? Did they believe force was necessary, or that a lethal threat was imminent? Were they sober, or does intoxication bar their mistaken belief?
Step 4: Apply the objective element.
Was the force proportionate (or not grossly disproportionate in a householder setting)? Would a sober person of reasonable firmness sharing relevant characteristics have acted the same way?
Step 5: Check for disqualifying factors.
Did the defendant have a safe opportunity to call the police or escape? Did they join a violent gang? Did they continue offending after the danger ended?
Step 6: Reach a clear conclusion.
State whether the defence will succeed, and conclude clearly on the defendant's criminal liability (i.e. whether they will be acquitted).