Defences
Self-defence/Prevention of Crime
Lesson Objectives
• I will be able to state the definition of the
defence of self-defence/prevention of crime
• I will be able to distinguish between selfdefence and prevention of crime
• I will be able to apply the rules to a given
situation
Self-defence/Prevention of Crime
• This topic is sometimes called public and private
defence. This is due to the fact that the common law
defence of self-defence is extended and, to some
extent superseded, by the statutory defence of
public defence (prevention of crime) under the
Criminal Law Act 1967, s3
• As the two do overlap, the idea of self-defence is still
relevant as it may be that a person is defending
themselves from someone who is not, in fact,
committing a crime, e.g. because that person is
insane
• Self-defence is just defending yourself or
another, whereas the statutory defence deals
with prevention of crime. These are two
separate defences
• The two overlap and are essentially the same
but should be treated separately
Criminal Law Act 1967, s3
• This section provides:
– 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
The following points need to be considered:
– The necessity of force
– The reasonableness of force
The necessity of force
• The basic principle is that the use of force is
not justified if it is not necessary. It will be
necessary if it is seen to be so in the
circumstances which exist or which the
defendant genuinely believed existed
• This is seen in Gladstone Williams (1987) – the
defendant believed a youth was being
attacked when in fact his victim was trying to
arrest the youth
Williams 1987
• This case shows that if D mistakenly believes
someone is being assaulted then self-defence may
be relied on even if there was no actual assault
• Even if the mistake is unreasonable
• S 76 clarifies that the mistake need not be
reasonable, but the more reasonable it is, the more
likely it was genuinely held
• However, the force must be reasonable in the
(mistaken) circumstances
• Pre-emptive strike – the defence comes into
operation even if the attack has not yet taken
place providing it is imminent – the defendant
does not have to wait to be attacked and can
strike the first blow – Bird (1985)
• The difficulty with this is establishing that the
force he uses is reasonable
• The defendant does not have a duty to retreat
as far as possible before using force – Bird
(1985)
The reasonableness of force
• The jury have the task of deciding whether, in all circumstances, the
defendant used reasonable force. The jury, of course, can take as long
as they need to balance the facts
• The defendant usually does it in a split second so he may use
excessive force
• Lord Morris of Borth-y-Gest said in Palmer (1971)
"If there has been an attack so that defence is reasonably necessary,
it should be recognised that a person defending himself cannot weigh
to a nicety the exact measure of necessary defensive action. If a jury
is of the opinion that in a moment of unexpected anguish the person
attacked did only what he honestly and reasonably thought was
necessary, that should be regarded as most potent evidence that only
reasonably defensive action was taken."
• Clegg (1995) and Martin (2001) demonstrate
the extremes to which a jury must go when
considering what amounts to reasonable force
Proportionality
•
The question of proportionality arises in the Criminal Justice and Immigration
Act 2008
•
Section 76(6) makes plain that the degree of force used by a person is not to
be regarded as having been reasonable in the circumstances as he believed
them to be if it was disproportionate in those circumstances
•
Guidance as to whether the degree of force used was reasonable in the
circumstances of a case can be found in s76(7) which provides:
a)
That a person acting for a legitimate purpose may not be able to weigh to a
nicety the exact measure of necessary action; and
b) That evidence of a person’s 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
Reasonable force
• S 76 Criminal Justice and Immigration Act 2008
explains the degree of force which can be used
• S 76 applies whether D is relying on the common
law defence of self-defence or the statutory
defence of prevention of crime
• Whether force is reasonable is decided by
reference ‘to the circumstances as D believed
them to be’
Other issues
• Under s 76 (5) D cannot rely on a mistaken
belief caused by voluntary intoxication
• If D is not intoxicated, the jury must decide
whether the force was reasonable based on
D’s perception of the facts (Williams)
• If it is excessive the defence fails – Clegg
• In Martin the farmer shot and killed a burglar
and seriously injured another. The jury
rejected self-defence as they were retreating
and there was clearly no threat
The 2 questions
• There are essentially 2 questions for the jury
• Did D genuinely believe force was necessary in
the circumstances? (What D believed; a
subjective question)
• Was the degree of force reasonable in those
circumstances? (An objective question)
• S 76 makes clear that the second is decided by
reference to the first
• This makes the decisions in Martin & Cairns
seem wrong
Summary
Did D honestly believe
that force was
necessary? Williams
Was the force
reasonable in the
circumstances?
Martin
Self-defence &
prevention of
crime
A mistaken belief is OK
A drunken belief
is not OK
Self-defence
Case Questions
Case 56 Questions
R v Williams (Gladstone) (1984)
1 What was the verdict in this case?

2 What defence had the defendant tried to rely on?
3 What mistake had the defendant made?
4 How should a person who has made a mistake as to the facts of a
situation be judged?
5 Does the defendant’s belief have to be reasonable?
6 What are the implications for the defendant if his or her belief is entirely
unreasonable?
Case 56 Answers
1 The defendant was found not guilty.

2 He tried to argue that he had acted in self-defence.
3 He had made a mistake as to the facts of the case and had thought —
incorrectly — that self-defence was required.
4 The court held that the defendant should be judged against the mistaken
facts as he honestly believed them to be.
5 No. The mistake does not have to be reasonable, as long as it is honestly
held by the defendant.
6 The defendant may rely on an unreasonable belief, as long as it was
honestly held. The more unreasonable the belief, however, the less likely
the jury is to believe that the defendant honestly held it.
Case 57 Questions
R v Bird (1985)
1 What was the verdict in this case?

2 Following this case, does a person have to retreat if possible or show
that he or she is not willing to fight?
3 Does a person need to wait to be attacked before he or she can use
self-defence?
4 Can a person prepare for a possible attack?
5 What happened in Attorney General’s Reference (No. 2) (1983)?
6 What happens if the defendant makes a mistake and wrongly thinks
that self-defence is necessary?
Case 57 Answers
1 The defendant was found not guilty.

2 No. This would mean that self-defence was only available to those who
were unable to retreat. In this case, the Court of Appeal said that there
may be situations when the defendant might react immediately without
retreating. The matter is one for the jury to consider.
3 No. Pre-emptive strikes are included within this defence, which means
that the defendant does not need to wait to be attacked before defending
himself or herself.
4 Yes. If the defendant believes that he or she is at risk from an attack on
his or her person or property, he or she may be able to make
preparations in order to defend himself or herself.
Case 57 Answers continued
5 The defendant’s shop had been attacked during riots. To try to prevent
this from happening again, he made petrol bombs that he intended to
use should he face attack in the future. However, there was no further
attack. The defendant was charged with breaching the Explosive
Substances Act 1883 by having an explosive substance in his possession.
He relied on self-defence and was found not guilty under the Act. On
appeal, his acquittal was upheld.
6 If a defendant makes a mistake and thinks that self-defence is necessary,
he or she will be judged on the facts as he or she honestly believed them
to be (R v Williams (Gladstone), 1984). This is still the case if the
mistake was unreasonable.
Case 58 Questions
R v Clegg (1995)
1 When can force be used?

2 What is the effect of a successful plea of self-defence?
3 Who has the burden of proof?
4 What test is used to determine whether force is reasonable?
5 Once the defendant has shown that force was necessary, what must he
or she prove in order to rely on the defence?
6 Why was the defendant in this case unable to rely on self-defence?
Case 58 Answers
1 Force can be used in order to:

defend oneself, another or property
prevent crime
arrest an offender
2 If a defendant is acting to protect himself or herself, another or property,
providing that the force used is reasonable, he or she has a complete
defence to any crime since the justifiable use of force means his or her
actions are not unlawful. Thus, if successful, he or she will be found not
guilty.
3 Once the defendant has raised the issue of self-defence or there is some
other evidence of it, it is up to the prosecution to prove beyond
reasonable doubt that the defendant was not acting in self-defence or
that the force used was unreasonable.
Case 58 Answers continued
4 The test is whether a person used such force as was objectively
reasonable in the circumstances as he or she believed them to be.
5 He or she must prove that the force used was reasonable in the
circumstances. The problem is that there is no definition of ‘reasonable
force’, and it is a matter for the jury to decide in each case. The jury
must take various factors into account including the threat of harm, the
urgency of the situation and any other options available to the defendant.
A lower degree of force will be expected if the defendant is protecting
property rather than people.
6 The firing of the shot that killed the passenger was found to be an
excessive use of force. The defence fails if a defendant uses a greater
degree of force than is necessary in the circumstances.
Extras
Topic 7
Self-defence
Self-defence
Introduction
There are three situations where the use of force may be justified:
Self-defence: this is a common-law defence, often termed ‘private
defence’, which also includes defence of another person and defence
of property.
Defence of property: this area is regulated partially by common
law and partially by statute, namely the Criminal Damage Act
1971.
Prevention of crime: this is a public or statutory defence covered
by the Criminal Law Act 1967, which states at s.3(1):
‘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.’
Self-defence
Elements (1)
• For force to be justified, it must have been necessary.
• The defendant is judged in the circumstances as he or
she honestly believed them to be.
• To decide whether force was necessary, the jury will
consider the surrounding circumstances.
• The force must also be reasonable – this is a matter for
the jury in each case.
Self-defence
Elements (2)
• Pre-emptive strikes are permissible, so a person does
not have to wait to be attacked before defending himself
or herself.
• A defendant can use threats of force or threats of death
in order to try to stop an attack on himself or herself, or to
prevent a crime.
• If the defendant believes that he or she is at risk of an
attack on his or her person or property, he or she may be
able to make preparations in order to defend himself or
herself.
Self-defence
Elements (3)
• A defendant is not under a duty to retreat.
• If a defendant makes a mistake and thinks that selfdefence is necessary, he or she will be judged on the facts
as he or she honestly believed them to be. This is still the
case if the mistake was unreasonable.
• If the defendant uses excessive force, the defence will
fail.
Self-defence
Evaluation (1)
The ‘all or nothing’ effect
A situation may arise where some force is justified but the
defendant uses too much. This means that the defence
fails and critics have argued that this can lead to unfair
results. For some offences, the need for some force can be
taken into account when sentencing the defendant. In
murder cases, however, the mandatory nature of the
sentence means that this is not possible and the defendant
will be convicted and sentenced to life imprisonment.
Self-defence
Evaluation (2)
Intoxication
The current rule is that a defendant will not be able to rely
on a mistaken belief that self-defence is required if that
mistake has been made due to intoxication. This has been
criticised as being too harsh, particularly given that
intoxication is a defence to specific intent crimes.
Self-defence
Reform (1)
Allow an alternative conviction of manslaughter
To combat criticism of the ‘all or nothing’ nature of the
defence, it has been suggested that where some force is
justified but the defendant uses too much and causes the
death of the victim, it should be open to the jury to convict
him or her of manslaughter rather than murder. This
argument was rejected in Clegg, but the Law Commission,
in its consultation document ‘Partial Defences to Murder’
(2003), suggested that this area needs to be re-examined.
Self-defence
Reform (2)
Change the ruling in O’Grady
The rule in O’Grady is seen by some as too harsh, and it
has been suggested that mistakes as to the need for selfdefence induced by intoxication should operate as a
defence.