Revise Defences for Cambridge 9084 (4.4.1)

In the law of tort, a defence is an argument raised by the defendant which, if successful, can absolve them of liability, either completely or partially. Once the claimant has established the elements of a tort, the burden of proof shifts to the defendant to establish a valid defence on the balance of probabilities. Defences are broadly categorised into two types: complete defences and partial defences. A complete defence, such as 'volenti non fit injuria' (consent) or statutory authority, will defeat the claim entirely, and the claimant will receive no damages. A partial defence, most notably contributory negligence, results in a reduction of the damages awarded to the claimant, reflecting their own contribution to the harm they suffered.

Volenti non fit injuria, meaning 'no injury is done to one who consents', is a complete defence. For it to succeed, the defendant must prove three elements. First, there must be an agreement to the risk, which can be express or implied from the claimant's conduct. Second, the claimant must have had full knowledge of the nature and extent of the risk; it is not enough to know there is a risk, as established in Smith v Charles Baker & Sons (1891). Third, the claimant's acceptance of the risk must be voluntary and free from any compulsion. For example, in Haynes v Harwood (1935), a rescuer was not considered to have acted voluntarily. The defence is severely limited in road traffic accidents by s.149 of the Road Traffic Act 1988.

Contributory negligence is a partial defence governed by the Law Reform (Contributory Negligence) Act 1945. It applies where the claimant's own lack of care has contributed to the damage they suffered. The court will reduce the claimant's damages by a percentage it deems 'just and equitable'. The test involves two questions: first, did the claimant fail to exercise reasonable care for their own safety? This is an objective test. Second, did this failure contribute to their injury? For instance, in Froom v Butcher (1976), failing to wear a seatbelt was deemed contributory negligence as it contributed to the claimant's injuries, not the accident itself. The extent of the reduction depends on the claimant's share of responsibility for the damage, with courts considering the relative blameworthiness of both parties.

The defence of necessity applies in rare situations where the defendant has intentionally committed a tort in order to prevent a greater harm from occurring. It is a difficult defence to establish, particularly where it causes personal injury. It can be divided into public necessity (acting for the general good, e.g., pulling down a house to create a firebreak) and private necessity (acting to protect one's own interests). In Cope v Sharpe (No 2) (1912), setting fire to land to create a firebreak to protect the defendant's property from a spreading fire was justified. However, the defence failed in Southwark LBC v Williams (1971) for homeless people squatting, as the courts feared it would open the floodgates to similar claims.

Statutory authority is a complete defence which provides that if a defendant's actions are authorised by an Act of Parliament, they cannot be sued in tort for any consequences that are an inevitable result of that authorised act. This is often relevant in cases of nuisance. In Allen v Gulf Oil Refining Ltd (1981), residents complained of noise and vibrations from an oil refinery. The House of Lords held that the construction of the refinery was authorised by statute, and the nuisance was an inevitable consequence of its operation, thus providing a defence. However, the defence will fail if the harm could have been avoided through the exercise of reasonable care, as the authority does not extend to negligent performance of the statutory duty (Geddis v Proprietors of Bann Reservoir).

This defence, meaning 'from a dishonourable cause an action does not arise', prevents a claimant from recovering compensation for loss suffered while engaged in illegal activity. It is a complete defence based on public policy. The modern approach was established by the Supreme Court in Patel v Mirza (2016), which introduced a flexible 'trio of considerations':

1. Purpose of the prohibition: What was the purpose of the law the claimant broke, and would denying the claim help enforce that purpose?
2. Other public policies: Are there other public policies that might be affected by denying the claim?
3. Proportionality: Would denying the claim be a proportionate response to the illegality? The court considers the seriousness of the conduct, its centrality to the tort, and whether it was intentional. This replaced the stricter, more uncertain previous rules. For example, in Pitts v Hunt (1991), a claim by a passenger who encouraged a drunk, uninsured, underage driver was defeated by illegality as they were engaged in a joint criminal enterprise. The Patel test aims to avoid unjust outcomes while upholding the integrity of the legal system.