The general rule is that all relevant evidence is admissible in criminal proceedings. However, there are important exceptions where evidence that is technically relevant will be excluded because admitting it would be unfair or contrary to the public interest. You need to understand these exclusionary rules because they are central to ensuring a fair trial and upholding the integrity of the criminal justice system.
There are three main routes by which evidence can be excluded. First, section 78 of PACE 1984 gives the court discretion to exclude prosecution evidence obtained unfairly. Second, Article 6 of the ECHR provides a right to a fair trial which can render evidence inadmissible. Third, the court's inherent jurisdiction allows it to stay proceedings as an abuse of process where a fair trial is no longer possible.
In an exam question, always consider all three exclusion routes. The prosecution may argue s.78 is enough, but the defence should raise Article 6 and abuse of process if the facts support it. Each route has a different test and a different remedy, so getting the right one matters.
In any proceedings the court may refuse to allow evidence on which the prosecution proposes to rely, if it appears to the court that, having regard to all the circumstances, including the circumstances in which the evidence was obtained, the admission of the evidence would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it.
Section 78 applies to ALL evidence on which the prosecution proposes to rely, not just evidence obtained by the police. It covers evidence obtained by private individuals, undercover agents, and even evidence obtained abroad. The discretion applies only to prosecution evidence - the defence cannot use s.78 to have its own evidence excluded.
The court applies a two-stage test under s.78. First, it considers all the circumstances, including how the evidence was obtained. Second, it asks whether admitting the evidence would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it. This is a high threshold - the unfairness must be significant enough to undermine the trial itself.
Section 78 does not automatically exclude evidence obtained improperly. The court exercises a discretion and must weigh the unfairness of admitting the evidence against the public interest in convicting the guilty. Even serious misconduct by the police will not always lead to exclusion if the evidence is crucial and reliable.
Unfair conduct covers a wide range of behaviour by police officers and others acting on behalf of the state. It includes oppression, inducement, trickery, failure to follow proper procedures, and breaches of PACE codes. The conduct does not have to be deliberate - even careless or negligent behaviour can trigger s.78 if it results in unfairness.
Oppression includes physical or psychological pressure applied to a suspect to obtain evidence. Inducement means offering a benefit or making a threat to get someone to confess or cooperate. In R v Sang (1980), the House of Lords confirmed that the trial judge has a discretion to exclude evidence obtained by trickery, although the general principle is that the court is not concerned with how evidence was obtained.
If a suspect is not properly cautioned before being questioned, any answers they give may be excluded under s.78. The right to a caution is set out in Code C of PACE. However, failure to caution does not automatically lead to exclusion. The court will consider whether the defendant was aware of their right to remain silent and whether the evidence was reliable.
PACE is accompanied by several Codes of Practice (Codes A-G) which set out how police should carry out their powers. The Codes cover stop and search, detention, questioning, identification, and more. A breach of the Codes does not itself make evidence inadmissible, but it is a relevant factor under s.78 when the court considers whether the admission of evidence would be unfair.
Not every breach of the Codes will lead to exclusion. The court will look at how significant the breach was. A minor or technical breach is unlikely to tip the balance. But a serious breach that goes to the heart of the fairness of the proceedings, such as denying a suspect access to legal advice or failing to record an interview, is much more likely to lead to exclusion under s.78.
A breach of the Codes is NOT automatically fatal to the prosecution case. It is a factor that the court takes into account under s.78. The defence must show that the breach was significant and that admitting the evidence would have an adverse effect on the fairness of the proceedings.
Entrapment occurs when a state agent (usually an undercover police officer) incites or induces a person to commit an offence that they would not otherwise have committed. This is different from a controlled operation, where police simply provide an opportunity for a person who is already willing to commit an offence. The key distinction is between providing an opportunity and planting the criminal idea.
Evidence obtained through entrapment can be excluded under s.78. In R v Looseley (2001), the House of Lords held that where the police have lured a person into committing an offence, the court may stay the proceedings as an abuse of process or exclude the evidence under s.78. The court must ask whether the police acted as agents provocateurs or merely provided an opportunity for the commission of an offence.
Entrapment is NOT a substantive defence in English law. A defendant cannot simply plead entrapment and be acquitted. Instead, entrapment is relevant to the court's discretion to exclude evidence or stay proceedings as an abuse of process. The defendant still has to face the charges.
If there is a significant delay between the alleged offence and the defendant being charged, this can prejudice the defendant's ability to get a fair trial. Witnesses' memories fade, evidence is lost, and the defendant has the charge hanging over them. The court can exclude evidence or even stay proceedings if the delay is unreasonable and has caused significant prejudice.
Delay before charge can be relevant under s.78 if it affects the fairness of the proceedings. For example, if the police delay interviewing a suspect and their memory of events has deteriorated, a confession obtained much later may be less reliable. The court will consider the length of the delay, the reasons for it, and whether it has prejudiced the defence.
In the determination of his civil rights and obligations or of any criminal charge against him, everyone is entitled to a fair and public hearing within a reasonable time by an independent and impartial tribunal established by law.
Everyone charged with a criminal offence shall be presumed innocent until proved guilty according to law.
Article 6 can operate as an independent ground for excluding evidence, separate from s.78 PACE. In R v Khan (Sultan) (1997), the House of Lords held that evidence obtained by a third party in breach of Article 8 (right to privacy) could not be excluded under the common law or s.78 because the police were not involved. However, after the Human Rights Act 1998, Article 6 itself provides a standalone basis for exclusion if admitting the evidence would make the trial unfair.
Under Article 6, evidence must be excluded if its admission renders the trial as a whole unfair. This is a stricter test than s.78. The question is not whether the evidence was obtained unfairly, but whether the trial itself would be unfair if the evidence were admitted. The focus is on the overall fairness of the proceedings, not just the manner in which the evidence was obtained.
In practice, defence advocates will often argue both s.78 and Article 6. If the judge excludes the evidence under s.78, the Article 6 argument does not need to be decided. But if the judge admits the evidence under s.78, the defence can argue that Article 6 nonetheless requires exclusion because the trial would otherwise be unfair.
The court has an inherent jurisdiction to stay proceedings as an abuse of process. This is the most drastic remedy available because it ends the case entirely, rather than simply excluding a piece of evidence. A stay will only be granted in the most serious cases where no lesser remedy (such as excluding evidence or giving a warning to the jury) would be sufficient to ensure a fair trial.
There are two main categories of abuse of process. First, where it is impossible to give the defendant a fair trial (as established in R v Maxwell (2010)). Second, where it would be unfair to put the defendant on trial at all, even if a fair trial were technically possible (as established in R v Grant (2005)). The second category includes cases of entrapment, delay, and double jeopardy.
The distinction between an entitlement to a stay and a discretionary stay is important. If the court finds that a fair trial is impossible (Maxwell), the defendant is ENTITLED to a stay - the court has no choice. If the court finds that it would be unfair to try the defendant even though a fair trial is possible (Grant), the stay is discretionary - the court weighs the factors and decides. This distinction affects how you frame your arguments.
| Type | Test | Remedy | Example |
|---|---|---|---|
| Impossible fair trial (Maxwell) | Can the defendant receive a fair trial? | Entitled to a stay | Evidence destroyed, witnesses deceased |
| Unfair to try (Grant) | Is it fair to prosecute at all? | Discretionary stay | Entrapment, excessive delay |
| Double jeopardy | Has the defendant already been tried? | Abuse of process | Retrial after acquittal without new evidence |
| Vexatious prosecution | Is the prosecution brought for an improper purpose? | Discretionary stay | Prosecution to harass the defendant |
In R v Looseley (2001), the House of Lords confirmed that entrapment can lead to a stay of proceedings as an abuse of process. Where the police have acted as agents provocateurs by inciting a person to commit an offence they would not otherwise have committed, it may be an abuse of process to allow the prosecution to continue. The court considers whether the police conduct was so serious that it would be unfair to allow the prosecution to proceed.
Excessive delay can amount to an abuse of process under the Grant category. If the prosecution has delayed unreasonably in bringing the case, and the defendant has suffered significant prejudice (such as faded memories, lost evidence, or the stress of having proceedings hanging over them), the court may stay the proceedings. The court balances the prejudice to the defendant against the public interest in prosecuting serious offences.
The rule against double jeopardy means a person cannot be tried twice for the same offence. This is a fundamental principle of English law. However, the Criminal Justice Act 2003 created limited exceptions where a person who has been acquitted can be retried if "new and compelling evidence" comes to light. Attempting to prosecute someone a second time without such evidence would be an abuse of process.
When deciding whether to exclude evidence, the court must balance the public interest in convicting the guilty against the defendant's right to a fair trial. This is never a straightforward exercise. The more serious the offence, the stronger the public interest in admitting the evidence. But the more serious the misconduct, the stronger the case for exclusion. You need to weigh both sides of the argument.
Section 78 and Article 6 overlap but are not identical. Section 78 is the primary statutory route for excluding unfairly obtained evidence. Article 6 provides an additional, constitutional layer of protection. In most cases, if evidence is excluded under s.78, there is no need to consider Article 6. But Article 6 may catch situations that s.78 does not, such as evidence obtained by a private individual.
In practice, the defence should raise s.78 first because it is the most flexible tool. If the judge excludes the evidence, there is no need to go further. If the judge admits the evidence under s.78, the defence can then argue Article 6 as a fallback position. If both fail, the defence can argue for a judicial warning to the jury or, in extreme cases, a stay of proceedings as an abuse of process.
Sometimes the evidence is not so unfairly obtained that it must be excluded, but the jury should be warned about its reliability or the circumstances in which it was obtained. A judicial warning is a middle ground between full admission and full exclusion. The judge tells the jury to treat the evidence with caution. This is often the appropriate remedy where there has been a minor breach of the Codes or the evidence is slightly unreliable.
A warning is appropriate where the unfairness is not so great as to require exclusion, but the jury needs to be aware of the circumstances. For example, if a suspect was interviewed without a caution but the evidence appears reliable, the judge might admit the evidence but warn the jury to treat it with caution. A warning is also appropriate where an identification procedure was flawed but not so badly that the evidence should be excluded.
A judicial warning is not the same as excluding evidence. The evidence is still before the jury, and the jury can still rely on it. The warning simply reminds the jury to be cautious. If the unfairness is serious, exclusion is the correct remedy, not a warning. You should not accept a warning as a substitute for exclusion where the evidence was obtained through serious misconduct.