9.4 Defences and Vicarious Liability

Once the claimant has a complete negligence (or other tort) case, the defendant may still reduce or defeat it. FLK1 lists three defences — volenti non fit injuria, contributory negligence, and illegality — and then principles of vicarious liability. Vicarious liability is not a defence; it is a route to a solvent defendant. Keep the two-stage UK Supreme Court analysis. Do not revive tests the Supreme Court has confined.

Volenti non fit injuria

Volenti is a complete defence: no injury is done to one who consents. The defendant must show that the claimant had full knowledge of the nature and extent of the risk and freely agreed to accept that legal risk, not merely that they knew the activity was dangerous.

Knowledge is not consent. An employee who continues to work with a known dangerous machine has not necessarily agreed to waive the employer's duty (Smith v Baker & Sons [1891] AC 325). Volenti rarely succeeds against employees. It can succeed where the claimant embraces an obvious extreme risk: flying with a drunken pilot after drinking together (Morris v Murray [1991] 2 QB 6). Drunken passengers in cars are more often dealt with by contributory negligence than by volenti.

Section 149 of the Road Traffic Act 1988 blocks volenti (and certain exclusion notices) in relation to passengers in vehicles that must be insured. On exam facts involving a passenger in a car, do not let volenti wipe out the claim. Rescuers who reasonably intervene are not treated as volunteers to the danger created by the defendant (Haynes v Harwood [1935] 1 KB 146). Sporting participants accept the inherent risks of the game played according to the rules, not a reckless assault dressed up as play. ICI Ltd v Shatwell [1965] AC 656 is the rare employment success: shot-firers ignored express instructions and statutory rules; they had truly consented.

Contributory negligence

The Law Reform (Contributory Negligence) Act 1945, section 1, allows the court to reduce damages to such extent as it thinks just and equitable having regard to the claimant's share in the responsibility. It is a partial defence. Pitts v Hunt [1991] 1 QB 24 confirms that a finding of 100% contributory negligence is not available: that would be a complete defence by another name, and the 1945 Act presupposes fault on both sides.

Froom v Butcher [1976] QB 286 still supplies the working figures for seat belts in England and Wales: 25% if wearing a belt would have prevented the injury entirely; 15% if it would have reduced the injury; nil if it would have made no difference. Similar structured reasoning is used for cycle helmets, though the percentages are not a separate statute. Children are judged by the standard of a reasonable child of their age (Gough v Thorne [1966] 1 WLR 1387). A very young child may bear no reduction. Failure to mitigate is related but distinct: it concerns unreasonable conduct after injury, not fault in the accident itself.

Illegality (ex turpi causa)

A claim may fail if allowing it would be inconsistent with the integrity of the legal system. Patel v Mirza [2016] UKSC 42 (a restitution case) replaced a rigid reliance test with a trio of considerations: the underlying purpose of the prohibition that was transgressed, any other relevant public policies, and whether denying the claim would be a proportionate response.

In tort, Henderson v Dorset Healthcare University NHS Foundation Trust [2020] UKSC 43 is the functioning illustration. A claimant who, during a psychotic episode, killed her mother and was convicted of manslaughter on the ground of diminished responsibility could not recover losses that flowed from the sentence and the conviction. The court applied Patel but also the consistency principle associated with Gray v Thames Trains Ltd [2009] UKHL 33. By contrast, Stoffel & Co v Grondona [2020] UKSC 42 allowed a conveyancing-negligence claim to proceed despite an unlawful mortgage background: the illegality was not a proportionate reason to strip the client of a remedy against a negligent solicitor.

Pitts v Hunt also shows two drunken motorcyclists on a joyride: the passenger's claim failed for illegality as well as running into the 100% contributory-negligence limit. On SQE1, ask whether the loss claimed is the product of the crime (sentence, confiscation, the inability to rely on one's own serious offending) or merely a background that is not central to the measure of loss.

Vicarious liability: two stages, current UKSC law

Vicarious liability makes D pay for a tort committed by X. D need not be at fault. Two stages must both be satisfied (Various Claimants v Barclays Bank plc [2020] UKSC 13; WM Morrison Supermarkets plc v Various Claimants [2020] UKSC 12; the relationship-plus-connection structure is restated in later UKSC authority including X v Lord Advocate).

Stage 1 — relationship. Historically this was employment. It now includes a relationship akin to employment (Various Claimants v Catholic Child Welfare Society (the Christian Brothers case) [2012] UKSC 56; Cox v Ministry of Justice [2016] UKSC 10; Armes v Nottinghamshire County Council [2017] UKSC 60). Lord Phillips listed five incidents that often justify the extension: the defendant is more likely to have the means to compensate; the tort is committed as a result of activity undertaken for the defendant; the activity is part of the defendant's business activity; the defendant created the risk by assigning the activity; and there is an element of control. Those factors help in doubtful stage-1 cases. They are not a free-standing overlay that abolishes the independent-contractor rule.

Barclays is the correction. A doctor engaged to examine job applicants, paid a fee per report, carrying on his own medical practice from his own premises, was an independent contractor. The bank was not vicariously liable for alleged sexual assaults during those examinations. The Supreme Court confirmed that a person in business on their own account is not in a relationship akin to employment merely because the bank arranged appointments and used a pro forma report. Do not tell the examiner that Christian Brothers replaced the independent-contractor rule.

Stage 2 — close connection. The question is whether the wrongful conduct was so closely connected with acts the employee was authorised to do that it can fairly and properly be regarded as done in the course of employment (Lord Nicholls in Dubai Aluminium Co Ltd v Salaam, adopted in Morrisons). Lister v Hesley Hall Ltd [2001] UKHL 22 shows that sexual abuse by a warden of a residential school can be closely connected with the authorised pastoral role.

Morrisons confines a looser reading of Mohamud v WM Morrison Supermarkets plc [2016] UKSC 11. An internal auditor, authorised to send payroll data to external auditors, copied the data and published it online as a personal vendetta. Vicarious liability failed. Employment that merely gives the opportunity to commit a wrong is not enough. Acting on a personal frolic, rather than furthering the employer's business, points against stage 2. The Court of Appeal had wrongly used the Christian Brothers stage-1 factors to decide stage 2. Do not repeat that error.

What not to do: recite the old Salmond formula (authorised acts versus unauthorised modes) as if it were the current test; treat course of employment as any act at work; apply akin-to-employment factors to a true independent professional; skip stage 1 because the tort is heinous; or treat Mohamud as if any customer-facing job makes the employer an insurer for every crime.

A worked fork: a supermarket employee attacks a customer. Ask first whether the attacker is an employee or in a relationship akin to employment. Then ask whether the assault was a way of carrying out authorised duties (a confrontation while serving, as later explained in the Morrisons reading of Mohamud) or an independent personal campaign. Then, separately, consider the employer's primary duty if the claimant is a fellow employee. Vicarious liability and primary liability can both appear on the same facts; they answer different questions.