Necessity

Introduction

This chapter examines **necessity**, one of the **defences** available in the law of tort. Necessity is a **specialised** and **narrow** defence that allows a defendant to justify an action which would otherwise be tortious — most commonly a **trespass to the person, to land, or to goods** — on the basis that the action was **necessary to prevent a greater harm**. You will learn the **three core elements** the defendant must establish — an **imminent threat of harm**, **no reasonable alternative action**, and **proportionality** between the harm caused and the harm avoided — together with its principal applications (**immediate danger** and **medical necessity**) and its **limitations**.

Assessment focus

For SQE1 FLK1, you must be able to **identify** when the defence of necessity is engaged and to **apply** its requirements to a realistic client scenario. Questions are single best answer questions (SBAQs): you will typically be given a factual situation — frequently a **medical emergency involving a patient who cannot consent**, or an **act taken to avert immediate danger** — and asked to select the defence most likely to succeed, or to assess whether the elements of necessity are satisfied. Be ready to **distinguish necessity from consent (volenti non fit injuria)**: consent depends on the claimant's agreement, whereas necessity applies precisely where consent is **absent or impossible**. This is a closed-book assessment — commit the three elements and the leading examples to memory.

Study tips

1) Memorise the **three elements**: (i) **imminent threat** of harm or damage; (ii) **no reasonable alternative** action available; (iii) **proportionality** — the harm caused must be proportionate to the harm avoided. 2) Remember necessity is a **narrow** defence, **rarely** available outside **trespass** cases (it is very difficult to invoke in **negligence**). 3) Master the **two key scenarios**: **immediate danger** (e.g. pushing someone clear of an oncoming bus) and **medical necessity** (life-saving treatment for an **unconscious** patient who cannot consent). 4) Distinguish **necessity from consent**: necessity operates where the claimant **cannot consent**; consent operates where the claimant **does** agree. 5) Note the **public policy** foundation of the defence, which gives the court significant **discretion** to refuse a claim where it would be unjust to allow it.