Illegality

Introduction

This chapter examines **illegality** as a defence in the law of tort. The defence is also known by its Latin maxim **ex turpi causa non oritur actio** — 'no action may arise from a base (illegal) cause'. Where the defence succeeds it operates as a **complete defence**, barring the claimant's claim entirely. It applies where the claimant's cause of action is **closely linked to their own illegal or criminal conduct**. Crucially, however, the defence is **not a blanket rule** that bars every claim touching on illegality: the courts apply it **judiciously**, weighing the purpose of the rule infringed, the relevant public policy considerations, and the **proportionality** of denying the claim, following the approach laid down in **Patel v Mirza [2016] UKSC 42**.

Assessment focus

For the SQE1 FLK1 assessment you must understand how the **illegality defence** operates in tort and when a court will refuse a claim because of the claimant's own wrongdoing. You should be able to state and apply the **three-stage test** from **Patel v Mirza** (purpose of the rule infringed; public policy considerations; proportionality), identify the **factors relevant to proportionality**, and recognise the **three key elements** of the defence identified by **Sir Murray Stuart-Smith in Vellino v Chief Constable of Greater Manchester Police**. SQE1 questions are single best answer questions (SBAQs) set in **realistic client-based scenarios**; you will be expected to **apply** the defence to facts rather than merely recall the test. This is a **closed-book** assessment, so you must be able to recall the leading authorities — **Patel v Mirza**, **Pitts v Hunt**, **Vellino** — and the statutory limit in the **Road Traffic Act 1988** from memory.

Study tips

1) Memorise the **maxim**: ex turpi causa non oritur actio — illegality is a **complete** defence. 2) Learn the **three-stage Patel v Mirza test** in order: (i) purpose of the rule infringed; (ii) public policy considerations; (iii) proportionality. 3) Memorise the **four proportionality factors**: severity of the illegality; centrality of the illegality to the events; whether the illegality was intended; disparity in culpability between the parties. 4) Note that **Patel v Mirza was a contract case**, but the test is now applied across tort too. 5) Remember the **three Stuart-Smith elements from Vellino**: close link to the criminal act; public policy (judicial discretion, not a right); severity of the criminal conduct. 6) Distinguish illegality from **consent (volenti)**: an exclusion of liability for death or personal injury caused by negligence is **not** rendered valid merely because the claimant consented — see **section 149 of the Road Traffic Act 1988**.