Define: Necessity

Necessity, in legal terms, is a defence used to justify actions that would otherwise be considered unlawful or wrongful. It arises when an individual faces an emergency situation or imminent harm, and their actions are deemed necessary to prevent greater harm or danger. The necessity defence typically requires that the harm caused by the action is less severe than the harm that would have occurred if the action had not been taken. This defence is often invoked in situations such as self-defence, defence of others, or to prevent a greater public harm. However, the application of the necessity defence can vary depending on jurisdiction and the specific circumstances of each case.

In English law, necessity does not amount to a general defence either to a criminal charge or to a claim in tort. That is, the defendant cannot rely on the fact that he did what he did to avert an even worse outcome. Of course, there are specific variations of ‘necessity’ that do afford a defence, either in a crime, in tort, or in both. Self-defence, for example, is a complete defence in either branch of law. It is a defence to a criminal charge that the action was necessary to prevent another crime. There is another class of situation sometimes recognized by the criminal courts under names such as ‘duress of circumstances. These are situations where the defendant was not actually threatened with violence but had to take illegal measures to remove himself from a situation of violence.

These specific circumstances aside, necessity has traditionally not offered much hope to the defendant. Lord Denning famously remarked that if the driver of a fire engine failed to stop at a red traffic signal, he would not be protected from a criminal conviction merely because he was on the way to rescue someone from a blazing fire.

It isn’t hard to see the policy factors that are at work here. If the courts admit the acceptability of breaking the law to avoid some unpleasant outcome, it is ultimately going to be difficult to determine the boundaries of such a defence. What about a person who fails to stop at a red traffic signal because he knows that if he is late for work one more time, he will get fired, and his family will be cast into penury? What about the person who fails to stop at a red traffic signal because waiting at traffic signals makes him tense, and tension is bad for his health? Other ‘hard cases’ that have come before the courts include those in which homeless people have broken into unoccupied buildings to avoid freezing to death in the street and those where people have had to steal to avoid starvation. In most, if not all, of these cases, necessity was no defence.

The archetypal necessity case for many years was RVDudleyAndStevens1884, in which it was held that it was never acceptable to kill another person to save one’s own life (except in the special cases mentioned above, such as self-defence), even when the victim would inevitably die within days. However, more recently, there has been what appears to be a slight increase in the scope of the defence of necessity. In FVWestBerkshireHealthAuthority1990, it was deemed acceptable to sterilise a young woman who was mentally incapable of consenting to the procedure. This action would, of course, be an assault, and a serious one. It was held that it would be in the woman’s best interest to carry out the procedure, taking all the circumstances into account. Then we had the ghastly case of re-aconjoined twins (2001). This case concerned an action that could very likely have amounted to murder, but for the defences available to the medical practitioners. The reasoning of the Court of Appeal in this case is not always particularly clear, since all three judges seemed to decide on different grounds. What is clear, however, is the desire of the court to do the right thing without extending the defence of necessity any further than—pardon the pun—necessity requires.

What appears to have come out of the necessity cases of the last ten years is that there are circumstances in which the courts will recognise a defence of necessity, but it isn’t always easy to predict what these circumstances are. All the successful uses of the defence have involved unusual and extreme situations, which are hard to generalise.

This site contains general legal information but does not constitute professional legal advice for your particular situation. Persuing this glossary does not create an attorney-client or legal adviser relationship. If you have specific questions, please consult a qualified attorney licensed in your jurisdiction.

This glossary post was last updated: 10th April, 2024.