LAW03: Criminal Law (Offences against the Person) Defences

Self-defence/prevention of a crime

This defence covers the actions needed to defend yourself or another.

Plus there is a statutory defence of prevention of a crime under s. 3(1) Criminal Law Act 1967:

"a person may use such force as is reasonable in the circumstances in the prevention of a crime."

Was force necessary?

This is a question for the jury and will depend on the individual circumstances in each case.

So, if someone comes at you with a knife then obviously force will be necessary but if they just tap

you on the shoulder force will not be necessary.

Mistaken use of force

If the D has made a mistake about what is happening to them/in front of them then it is more

difficult to decide if force is necessary or not.

If the D has made a genuine mistake the jury must decide if force was necessary in the circumstances

as the D believed them to be.

If the jury believe the D honestly thought he was being threatened etc. then he can have a defence.

Genuine mistake

In a situation such as this the D must be judged on the facts as he genuinely believed them to be. Even

if the genuine mistake was unreasonable!

Williams (1987)

The D was on a bus when he thought he saw a man assaulting a youth. In fact the man was trying to arrest the youth for mugging an old lady. The D got off the bus and asked what was happening, the man said he was a police officer and was arresting the youth. The D then asked for ID but the man had none and so the D struggled with the man and injured him.

The D's conviction was quashed because the jury should have been allowed to consider the genuine mistake of the D and a possible defence of protection of another.

The decision in Williams (1987) can now be seen in s. 76 Criminal Justice and Immigration

Act 2008 (CJIA2008).

If the D has made a genuine mistake of the facts, he is to be judged on what he believed the facts to

be.

Drunken mistake

s. 76(5) CJIA2008 states that the D cannot rely on a mistake if it was made because of voluntary

intoxication.

Degree of force

The amount of force that can be used is explained in the CJIA2008.

It states that in deciding whether the force used is reasonable in the circumstances ...

a) that a person acting for a legitimate purpose may not be able to weigh to a nicety the exact measure of any necessary action; and

b) that evidence of a person having only done what the person honestly and instinctively thought was necessary for a legitimate purpose constitutes strong evidence that only reasonable action was taken by that person for that purpose.

So, if the D is facing an attack they are likely to be under stress and will not necessarily be able to gauge exactly how much force they should use.

If the D "honestly and instinctively" thought the force was necessary in the circumstances then this is

strong evidence that it is!

But if the force is used after all danger has passed then the defence will not be available.