Self defence law

This article was written as an opinion of the originator, in the country for which it was written. It is meant only as a guide and was considered to be accurate at the time of writing, in the country of origin. It should not be referenced as legal defence as it's current accuracy cannot be verified.

The Law on Self Defence


The following lecture is a practical guide on the law pertaining to Self Defence as it applies to Northern Ireland.

It cannot be relied upon as a definitive guide to the law and it is recommended that professional advice is obtained before relying on the information supplied anywhere within these notes.

By way of introduction the right of self (or private) defence is not set out in any specific legislation.

The right exists by virtue of Common Law (i.e. Judge made law as contained in cases). In addition S.3 of The Criminal Law (NI) Act 1967 (hereinafter S.3) allows the following,

"A person may use SUCH force as is reasonable in the

circumstances in the prevention of crime, or in effecting

or assisting in the lawful arrest of offenders or suspected

offenders or of persons unlawfully at large."

This is the only piece of legislation which codifies when and how the right to Self Defence can be used.

Assault and Battery

Before we can delve into S.3 further it is necessary to look at the technical definitions of assault and battery, in order to fully appreciate the Section's full implications.

(1) Assault:-

This offence is committed where D intentionally or recklessly causes the victim to apprehend immediate force. There does not need to be actual physical contact. It is enough that D's conduct causes the victim to think that force is about to be applied there and then.


Pointing a gun at the victim

Throwing a stone at the victim

Waving your fist under the victim's nose.

If the victim knows the gun is unloaded or that the threatening actions are unseen then there is no technical assault as the victim has to apprehend violence to themselves.

However, following on from this, if the victim is in fear of immediate violence, it is irrelevant that, unknown to him, there is in fact no danger of the threat being carried out (e.g. D points an unloaded or imitation gun).

Another main factor to constitute assault is that there has to be an apprehension of immediate violence e.g. "I will get you tomorrow." i.e. a future threat, does not constitute assault. However, courts are slowly changing e.g. stalking cases, letters through mailbox - assault can occur as long as they induce the requisite fear.

Finally a conditional threat ("Your money or your life") can constitute an assault.

Although the words clearly tell the victim that he has nothing to fear provided he does as he is told, D has no right to fetter the victim's freedom in this way and therefore an assault is committed.

A court looks at the act of assault as to whether the action of D caused an intention to create in the victim the expectation of the immediate application of force to him or recklessness in that D's action may cause the victim to believe that D is about to apply force (e.g. imitation gun).

(2) Battery:-

The least touch of a victim's body constitutes a battery. Again it can be intentional or reckless.

There therefore has to be the requirement of actual physical contact.

Assault and battery can be negated in several situations:-


Medical treatment where consent is given.


Physical sports -where the participants are aware, or ought to be aware, that contact can occur - though an offence can occur where one participant goes beyond the boundaries of the sport in hand.


Dancing, etc.

Other offences include:

(a)Common Assault

(b)Assault occasioning actual bodily harm (e.g. bruising)

(c)Grievous Bodily Harm (breaking the first two layers of skin).

Self Defence

As stated previously the law, or lack of it, is contained within S.3 of the 1967 Act. This permits a person to use such force as is reasonable in the circumstances. Having considered the definitions of assault and battery S.3 enables a person to defend oneself in situations where no force is applied but there is a real and immediate threat.

The force used to prevent physical harm. or a crime must be necessary in the circumstances. You cannot act in retaliation or to teach the aggressor a lesson. Once you enter this territory you cannot use 8.3 as a defence and you will be guilty of an offence.

E.g, D assaults P in the street. P defends himself and D runs off. Self Defence can be applied. However P runs after D, catches up with him and assaults him, P is guilty of an offence.

D assaults P with a knife. P defends himself, and removes the knife so D is unarmed. P then uses the knife on D. Again P is guilty of an offence. To use the knife himself would go beyond reasonable force :in the circumstances since D is now unarmed. Once P removed the knife he should throw it away.

Following on from before, if D uses a knife or a gun , P, under :immediate threat, may be excused if he uses a weapon (e.g. brush, kitchen knife) in order to defend himself. However, multiple stab wounds or worse on D may be overboard!

Self Defence and Lawful Force

Self Defence against Lawful Force, i.e. a police officer arresting someone in the course of his duty and where reasonable force is applied, is not an available defence. Of course, even when one can argue Self Defence in cases where police officers are acting unlawfully and using unreasonable force, then there is the problems of convincing a Court that you were acting within the scope of S.3.

Duty to Retreat

Common law once held that a person had a duty to retreat and could only use reasonable force to defend when "his back was against the wall".

This duty no longer applies and a person is not to be deprived of his right of self defence. However the courts will expect a person to demonstrate by his actions that he does not want to fight. A failure to retreat is only an element in the Courts considerations on which the reasonableness of a person's conduct is to be judged when self-defence is raised.

Pre-emptive Strikes

With regards to the technical definition of assault a person can, in effect, strike first in order to defend. Again it must be reasonable force and the onus is on you to show that, in the circumstances, it was reasonable.

E. g. D comes up to you in a threatening manner, lifts his hand to punch but you strike first.

What is Reasonable Force?

Traditionally 'reasonable force' embraces two elements:



i.e. that the force used was necessary in the sense that lesser violence would not have been adequate to defend oneself or prevent crime.



i. e. that it was reasonable to use that necessary force in the sense that it was not disproportionate to the mischief sought to be avoided. (See examples above).

In legal terms, what amounts to reasonable force is a question of fact for the jury (or judge) and not a question of law. The test is objective and depends on the jury's view of whether a reasonable person would have used such force in the circumstances as perceived by the accused.

Courts do take a practical view and recognise that the accused will have no time to consider his reaction.

Whilst the legal test is objective the courts allow a subjective element in that if the accused believed he was genuinely acting defensively and only doing what he thought was necessary for that purpose. However, he has no defence if he was acting offensively.

How to Plead Self Defence

A further consideration to be borne in mind is that, following an incident whereby Self-defence is pleaded, it will be some considerable time before a Court hears the facts.

It is therefore essential that at the time the incident occur all material facts are recorded by the appropriate authorities (police, lawyers, doctors).

The following steps should be considered in an "ordinary assault" situation.


Following the event, even though you have been able to defend an attack report the matter to the police. Provide a full statement of facts, in particular the way you were approached, that you believed you were under imminent attack, that you acted in self-defence, and that you used reasonable force.

It is very important to use and stress the words Self-Defence.


If injured report to Casualty or your GP and again ensure all your injuries are properly recorded and provide a brief history of the incident.


Contact your solicitor to ensure you have fully complied with your duties to report etc. You may also be able to lodge a claim with the Compensation Agency depending on the seriousness of the injuries you have sustained.


If you do not report to the police simply on the basis you firmly believe you were in the right there is no guarantee that your attacker may not do likewise in order to falsify the facts with a view to maximising any possible personal injury claim.


If you are arrested or requested to attend voluntarily ensure that you are accompanied by your solicitor. They will be able to advise you and ensure the interview is conducted properly. Please bear in mind that it is these initial stages that will determine a Courts finding of you later.

Ensure all relevant facts are provided.

The Effects of The Defence

If the defence succeeds then your conduct is regarded as being lawful and you will be acquitted or the charges simply dropped.

It can be used as a defence to any crime including murder.

However, it cannot be stressed enough, that if you act in self-defence or the prevention of crime but use more force than is reasonable in the circumstances, you will be convicted. The fact that you acted in self-defence will be taken into consideration and will be reflected in a lesser sentence that would otherwise apply. (This does not apply in the case of murder).

Finally, whilst the law and Courts will permit as much leeway as possible in cases where Self-defence is pleaded, it is for the Law to prescribe the standard of reasonable force in the circumstances, and if you get it wrong and act excessively, then you will be convicted.