Relevance and admissibility
Evidence should always be relevant, reliable and admissible. However, this is not always the
case. There have been many cases where these simple rules have not been followed.
Improperly obtained evidence – entrapment
If the police are finding it difficult to secure evidence that will be admissible in court, they
can consider a technique where they act as 'agent provocateurs'. In other words, they
induce others to break the law so that they can secure a conviction. English law does not
allow a defence of entrapment, but in principle, such evidence may be excluded under
Section 78 Police & Criminal Evidence Act 1984 (PACE). An excellent example of this is the
case of Colin Stagg and the 'Lizzie' evidence.
There is no rule requiring the exclusion of evidence simply because it has been improperly
obtained. The judge has the discretion to exclude such prosecution evidence under both
common laws, which is law not contained in an Act of Parliament, and under statute. One of
the main statuary provisions is under Section 78 PACE 1984. There is also the European
Convention on Human Rights (ECHR), where Article 6 provides the right to a fair trial. The
defendant would argue that the entrapment was not fair.
The standard test for exclusion is whether the probative value of the evidence is less than its
prejudicial effect. In other words, is the evidence proven to be more helpful in establishing
the truth than be harmful, unnecessary, to the case?
Section 78 PACE gives discretionary power to judges and magistrates to exclude evidence on
which the prosecution proposes to rely if it appears that 'having regard to all the
circumstances, including the circumstances in which the evidence was obtained, the
admission of the evidence would harm the fairness of the proceedings that the court ought
not to admit it'.
Pre-trial silence
A suspect's failure to explain when questioned by the police under caution may allow the
jury at the trial to draw an inference of guilt under the Criminal Justice & Public Order Act
1994 (CJPOA). This applies even if the suspect has received legal advice. Inferences alone
cannot establish guilt; other evidence is needed.
Character evidence and past convictions
Under the Criminal Justice Act 2003, previous convictions are not automatically allowed as
evidence, but there are occasions when they are allowed to be given to the court. The
Criminal Justice Act provides several rules or 'gateways' or ways of introducing a defendant's
previous convictions is under Section 103 and includes matters relating to the question
whether the defendant has a propensity to commit offences of the kind with which they are
charged. This means they tend to commit crimes of the same description or offences of the
same category.