I’ve written two ‘omnibus’ posts to review some key legal issues.

In response to the post on driving and rule 306, a correspondent wrote ‘Would you consider a general post about Necessity?’  I’m happy to do that but note that much of the text below does appear in earlier posts and in my book Emergency Law (4th ed, 2013).

Necessity is a common-law doctrine (that is it has been developed by the judges on a case by case basis) rather than the subject of legislation.  The gist of necessity is that where a person is caught on a dilemma of obeying the law and allowing some harm to occur, or to befall them, they can be excused from obeying the law.    The problem with a doctrine put as boldly as that, is that it is a licence for everyone to be judge in their own cause and to decide for themselves if the circumstances warrant disobeying the law.     That cannot be the law so the judges have developed tests as to when ‘necessity’ will apply, usually captured by that difficult concept of ‘reasonable’, to which there is added a concept of ‘proportional’.

Necessity is a defence to both the criminal law and the civil law, that is, if an action was ‘necessary’ to prevent a greater harm, that can be used to avoid both criminal charges and civil actions for negligence.  That can be seen to be relevant in context of this blog.  If necessity applies it can be a defence to criminal charges that might arise if you were to cut the roof off someone’s car, or touch them without consent.  It can also be a defence to a claim for damages arising out of the same conduct.

We can then look at the tests for necessity.

Criminal law

The starting point for most cases appears to be Stephen’s Digest of the Criminal Law (1st ed, 1887).   He said:

An act which would otherwise be a crime may in some cases be excused if the person accused can show that it was done only in order to avoid consequences which could not otherwise be avoided, and which, if they had followed, would have inflicted upon him or upon others whom he was bound to protect inevitable and irreparable evil, that no more was done than was reasonably necessary for that purpose, and that the evil inflicted by it was not disproportionate to the evil avoided. The extent of this principle is unascertained.

In R v Davidson [1969] VR 667 Menhennit J said ‘The principle of necessity as stated by Stephen contains within it the two elements of necessity and proportion’.   The accused has to believe, upon reasonable grounds, that it is necessary to take the action and that the harm done is not disproportionate to the harm to be avoided.

In R v Loughnan [1981] VicRp 43 Young, CJ and King, J said:

It will be seen from the statement by Sir James Fitzjames Stephen that there are three elements involved in the defence of necessity. First, the criminal act or acts must have been done only in order to avoid certain consequences which would have inflicted irreparable evil upon the accused or upon others whom he was bound to protect… The other two elements involved … can for convenience be given the labels, immediate peril and proportion…

In R v Dudley v Stephens (1884) 14 QBD 273 it was said that ‘necessity’ could not be a defence to murder.  In that case the accused was shipwrecked and along with his ship mates they drew straws whilst on the lifeboat.  The loser was killed and eaten. When the survivors were rescued they had survived because of they had eaten their shipmate but the fact that their death was otherwise imminent was no defence.

Even that rule has been doubted.  In Re A (Conjoined Twins) [2000] EWCA Civ 254 doctors and judges were faced with a dilemma.  Ward LJ described the facts:

Jodie and Mary are conjoined twins. They each have their own brain, heart and lungs and other vital organs and they each have arms and legs. They are joined at the lower abdomen. Whilst not underplaying the surgical complexities, they can be successfully separated. But the operation will kill the weaker twin, Mary. That is because her lungs and heart are too deficient to oxygenate and pump blood through her body. Had she been born a singleton, she would not have been viable and resuscitation would have been abandoned. She would have died shortly after her birth. She is alive only because a common artery enables her sister, who is stronger, to circulate life sustaining oxygenated blood for both of them. Separation would require the clamping and then the severing of that common artery. Within minutes of doing so Mary will die. Yet if the operation does not take place, both will die within three to six months, or perhaps a little longer, because Jodie’s heart will eventually fail.

The court authorised the surgery with the sure and certain knowledge that Mary would die and her death would be sooner than it would be without the operation.  The doctrine of necessity allowed that action in circumstances where the death of Mary would save Jodie but there was no sense of choice.  Whether the surgery went ahead or not, Mary would shortly die.  Without the surgery, Jodie would also die, with it she had good prospects.  This is not a situation like R v Dudley and Stephens where the person to die could have been anyone, and a person is not entitled to put their lives above others, that is no-one’s life in the life boat was more important than anyone else’s.  But where one person is fated to die regardless, hastening that person’s death to save others may be justified.  The court gave some examples. Brooke LJ said:

At the coroner’s inquest conducted in October 1987 into the Zeebrugge disaster, an army corporal gave evidence that he and dozens of other people were near the foot of a rope ladder. They were all in the water and in danger of drowning. Their route to safety, however, was blocked for at least ten minutes by a young man who was petrified by cold or fear (or both) and was unable to move up or down. Eventually the corporal gave instructions that the man should be pushed off the ladder, and he was never seen again. The corporal and many others were then able to climb up the ladder to safety.

In his third lecture, “Necessity and Duress”, Professor Smith evinced the belief at pp 77-78 that if such a case ever did come to court it would not be too difficult for a judge to distinguish R. v Dudley and Stephens. He gave two reasons for this belief. The first was that there was no question of choosing who had to die (the problem which Lord Coleridge had found unanswerable in R. v Dudley and Stephens at p 287) because the unfortunate young man on the ladder had chosen himself by his immobility there.

Robert Walker LJ said:

Of the many real and imagined examples put before the court it is worth mentioning two incidents which really did happen, although neither was the subject of a court decision. One is the awful dilemma which faced the commander of an Australian warship, in peacetime, when a very serious fire occurred in the engineroom. He ordered the engine room to be sealed off and flooded with inert gas, in order to save the ship and the rest of the crew, although the order meant certain death for anyone who was still alive in the engineroom. The other is the equally awful dilemma of a mountaineer, Simon Yates, who held his fellow-climber, Joe Simpson, after he had slipped and was dangling on a rope over a precipice at 19,000 feet in the Andes. Yates held Simpson for an hour, unable to recover him and becoming increasingly exhausted. Yates then cut the rope. Almost miraculously Simpson landed on a snowy ice bridge 100 feet below, and survived. When they met again Simpson said to Yates, “You did right”. This incident is mentioned in Professor Smith’s 1989 Hamlyn Lectures, Justification and Excuse in the Criminal Law, p.79.

At the end of Brooke LJ’s long and detailed judgment, His Honour referred again to Stephen’s text and said:

According to Sir James Stephen, there are three necessary requirements for the application of the doctrine of necessity:

(i) the act is needed to avoid inevitable and irreparable evil;

(ii) no more should be done than is reasonably necessary for the purpose to be achieved;

(iii) the evil inflicted must not be disproportionate to the evil avoided.

The point of this (from an academic point of view) simplified discussion of the principle is to show that it is a principle of law and can be applied to all offences, up to and including deliberate killing.   And although it is impossible to set out with certainty when it applies, the principles from 1887 remain the guide.


What does this have to do with the emergency services who do not go around deliberately killing people?  The point of mentioning in Re A is not that the emergency services have such terrible choices (but like the captain of the ship mentioned by Robert Walker LJ they may do) but to confirm that the principle is part of the common law of England and, I suggest, Australia.

And the principles will be relevant.  This often arises in the context of getting children out of locked cars – see Getting Children Out Of Locked Cars (February 23, 2016).  You can see the application.  A child is in a car in 40 degree heat.  Getting the child out is required to ‘avoid inevitable and irreparable evil’ ie the death or permanent injury of the child.  ‘No more should be done than is reasonably necessary for the purpose to be achieved’ which presumably involves breaking a window and unlocking the door, unless the road service organisation are there and can unlock the car.   And damaging the car is not disproportionate to the harm averted.    In that case, there’s a defence even though, prima facie, deliberately breaking someone’s car window is an offence.

For those in rescue squads you should realise that this is the same rule that allows you to cut the roof off the car that’s wrapped around the tree.  The driver isn’t consenting and you’re not allowed to just cut the roof off someone’s car, but if you do it to allow access to save their life all, of those principles again apply. If a child’s locked in a hot car, they need rescue as much as someone trapped in a mangled wreck.

Necessity might also be a defence to blocking a road.  It may be an offence to obstruct traffic but putting your car across the road and telling people that the road’s washed away, or blocked by an accident or fire because such an action is necessary to stop the next driver suffering harm, and the ‘harm’ done (obstructing traffic) is not disproportionate to the harm averted (stopping the driver going off a cliff or whatever).

So necessity is, in the right circumstances, a defence to a crime.


It is also a defence to a civil claim for damages.   Again it must be shown that there was a real and imminent danger and that the conduct of the defendant was such that “any reasonable man would, in the circumstances of the case, have concluded that there was no alternative to the act of trespass if the property [or life] endangered was to be preserved” (Cresswell v Sirl [1948] 1 KB 241, 247.

The doctrine can be traced back to Maleverer v Spinke (1538) 73 ER 79, 81 where the court said:

Yet we will well agree that in some cases a man may justify the commission of a tort, that is in cases where it sounds for the public good … a man may justify pulling down a house on fire for the safety of the neighbouring houses …

The doctrine of necessity can apply where the defendant reasonably believes that some action is necessary even if it turns out later that it was not. In Cope v Sharpe (No 2) [1912] 1 KB 496 the defendant was not liable for setting fire breaks that were not, as it turned out, necessary to control a fire that was extinguished by others before it got to the breaks.

In Proudman v Allan [1954] SASR 336, the South Australian Supreme Court summed up the application of the principle in cases where a person was taking action to save another’s property and in fact did more damage than would have happened if he hadn’t tried at all. It was said (at p 340):

In principle, there seems no reason why the common law should not recognise an exemption from liability to pay damages for trespass to goods of “volunteers” or strangers who, from no other motive than the same desire to save the property of others from damage or destruction as they would feel if it were their own property which was in jeopardy, take reasonable steps on an occasion of urgent necessity to remove that property out of the way of danger or safeguard it by some other means. It would seem that in principle the present respondent should not be absolutely liable for damage caused by his interference with the property of another when he acted in the reasonable belief that his interference was justified by the necessity of the situation and was intended to benefit the owner.

When the damage to property is necessary to save life, greater damage may be done that would be justified “to prevent mere damage to property” (Watt v Hertfordshire County Council [1954] 2 All ER 368; See also Rigby v Chief Constable [1985] 2 All ER 985, 994).

The safety of human lives belongs to a different scale of values from the safety of property. The two are beyond comparison and the necessity for saving life has at all times been considered a proper ground for inflicting such damage as may be necessary upon another’s property. (Southport Corporation v Esso Petroleum Co Ltd [1956] AC 218, 228).

In New Zealand it was said in Dehn v Attorney General [1988] 2 NZLR 564, 580 (Tipping J):

A person may enter the land or building of another in circumstances which would otherwise amount to a trespass if he believes in good faith and upon grounds which are objectively reasonable that it is necessary to do so in order (1) to preserve human life, or (2) to prevent serious physical harm arising to the person of another, or (3) to render assistance to another after that other has suffered serious physical harm.

In 2008 the High Court of Australia (Kuru v State of New South Wales (2008) 236 CLR 1, [2008] HCA 26, [40] (Gleeson CJ, Gummow, Kirby And Hayne JJ) said:

The common law has long recognised that any person may justify what would otherwise constitute a trespass to land in cases of necessity to preserve life or property. The actions of fire fighters, police and ambulance officers will often invoke application of that principle.

Necessity will justify almost any property damage in order to save life. The cutting up of the car, the entry onto property and the destruction of property can all be justified where that conduct is necessary to save another’s life. The doctrine is not limited to professional rescuers. A person visiting their neighbour who sees that they are lying injured on the floor is as justified in breaking the door in order to render assistance as is the local ambulance or fire service.

The law still requires that any action taken under the doctrine must be reasonable, so that if the rescuer acts in a way that is not reasonable in the circumstances, they may be liable in negligence (Beckingham v Port Jackson and Manly Steamship Co (1957) SR(NSW) 403).  This principle is subject to the rule that in deciding what was or was not reasonable, the courts, given the agony of the moment, are willing to excuse conduct that would be considered negligent in less urgent circumstances, particularly when life (rather than mere property) is involved.  The “agony of the moment” rule says that courts must take into account that where a person has found themselves in a situation not of their making and where immediate action is required, then the person’s conduct is not to be judged as negligent because, in retrospect, it appears that another course of action would have been better (Leishman v Thomas (1958) 75 WN(NSW) 173, 175):

[A] man is not to be charged with negligence if he, not being the creator of the crisis or emergency which has arisen, finds himself faced with a situation which requires immediate action of some sort and if, in the so called “agony of the moment”, he makes an error of judgment and takes a step which wiser counsels and more careful thought would have suggested was unwise.

A rescuer, “acting under the pressure of emergency, is to be judged leniently as to the reasonableness of his conduct” (Wallis v Town of Albany (1989) Aust Torts Reports ¶80-283, [69,011] (Pidgeon J); Wagner v International Railway Co 133 NE 437 (1921), 437-38 (Cardozo J)).

Necessity and medical treatment

This issue arose in In Re F [1990] 2 AC 1.  In that case the court had to consider whether doctors could lawfully sterilise a developmentally disabled adult.  Her parents wanted the procedure so that she did not have to deal with menstruation and the risk of pregnancy.  F was not competent to give consent and because of vagaries of the English law at that time, her parents could not give lawful consent.  The question was what doctrine could justify such a procedure.

Lord Goff again turned to necessity. The notion of ‘implied consent’ could not justify the action as you could not have implied consent from a person from who you could not get actual consent.    He said:

The basic requirements, applicable in these cases of necessity, that, to fall within the principle, not only (1) must there be a necessity to act when it is not practicable to communicate with the assisted person, but also (2) the action taken must be such as a reasonable person would in all the circumstance take, acting in the best interests of the assisted person.

On this statement of principle, I wish to observe that officious intervention cannot be justified by the principle of necessity. So intervention cannot be justified when another more appropriate person is available and willing to act; nor can it be justified when it is contrary to the known wishes of the assisted person, to the extent that he is capable of rationally forming such a wish.

As Lord Goff said ‘The principle is one of necessity, not of emergency’.  He gave these examples:

Take the example of a railway accident, in which injured passengers are trapped in the wreckage. It is this principle which may render lawful the actions of other citizens – railway staff, passengers or outsiders – who rush to give aid and comfort to the victims: the surgeon who amputates the limb of an unconscious passenger to free him from the wreckage; the ambulance man who conveys him to hospital; the doctors and nurses who treat him and care for him while he is still unconscious. Take the example of an elderly person who suffers  a stroke which renders him incapable of speech or movement. It is by virtue of this principle that the doctor who treats him, the nurse who cares for him, even the relative or friend or neighbour who comes in to look after him, will commit no wrong when he or she touches his body.

The two examples I have given illustrate, in the one case, an emergency, and in the other, a permanent or semi-permanent state of affairs. Another example of the latter kind is that of a mentally disordered person who is disabled from giving consent. I can see no good reason why the principle of necessity should not be applicable in his case as it is in the case of the victim of a stroke. Furthermore, in the case of a mentally disordered person, as in the case of a stroke victim, the permanent state of affairs calls for a wider range of care than may be requisite in an emergency which arises from accidental injury.


Necessity is a general and ill-defined doctrine.  It must be ‘ill-defined’ because the circumstances in which it may be applied are undefined.  But the doctrine does exist.  Where a person, whether a professional rescuer or not, believes and has some reason to believe that action is required to avoid an irreparable and grievous harm, they are justified in taking the action that they believe is necessary if they do no more than is required to achieve their objective and the harm done (which may be no more than to technically breach the law) is not disproportionate to the harm to be avoided.

You can see the doctrine’s relevance to the emergency services.  Breaking into a house or car to rescue someone is the example given by the High Court and the New Zealand court.  Providing care to those that cannot consent, the unconscious, children, the mentally ill or disabled etc are all things that the community at large, and the emergency services are called upon to do.   These things rarely get before a court but when they do it is the doctrine of ‘necessity’ that provides a general and broadly applicable doctrine to justify taking action to save a life or prevent harm.

The policy of the law, that when life is at stake it’s better to do something than nothing, is also behind my conclusion that if you have life saving skills you should use them, regardless of what uniform you are in.  It is also reflected in the good Samaritan legislation that was written to encourage people to act.