Principles and procedures to admit and exclude evidence - Ex...

Learning Outcomes

This article explains the operation and scope of the discretionary power to exclude prosecution evidence under section 78 of the Police and Criminal Evidence Act 1984 (PACE). You will be able to articulate the principles and procedures the courts use in determining whether to admit or exclude evidence, including:

• Explaining the legal test applied by courts under s.78 PACE 1984.
• Identifying the range of evidence and scenarios subject to the s.78 discretion, covering evidence obtained by police or investigators, including confession, physical evidence, and identification evidence.
• Recognising how improper or unlawful conduct by investigators, including breaches of PACE Codes, affect admissibility.
• Analysing the relationship of s.78 with mandatory exclusion (such as under s.76 PACE for confessions), with common law exclusionary discretion, and with human rights protection, particularly Article 6 of the European Convention on Human Rights.
• Applying s.78 principles to realistic examples, such as breaches of interview procedures, unlawful searches, or failures in the conduct of identification parades.
• Understanding the balancing of the public interest in crime detection and the need for trial fairness.
• Explaining how s.78 interacts with the exclusion of evidence on grounds of oppression, unreliability, entrapment, or abuse of process.

SQE1 Syllabus

For SQE1, you are required to understand the principles and procedures for admitting and excluding evidence under s.78 PACE 1984, with a focus on the following syllabus points:

• The scope, effect, and rationale of s.78 PACE 1984.
• Procedures for admitting and excluding evidence in criminal proceedings.
• Relevance and discretion in relation to evidence; differences between mandatory and discretionary exclusion.
• The operation of s.76 PACE 1984 for confessions, and the interplay with s.78 and the common law discretion.
• The legal framework on oppression, unreliability, and breaches of the PACE Codes of Practice.
• Human rights dimensions, especially Article 6 ECHR: the right to a fair trial, and how UK courts give effect to human rights requirements in evidence exclusion.
• Examples of unlawful or improper investigative methods, including denial of access to legal advice, breaches of procedures for vulnerable suspects, and failures in the conduct of identification procedures.
• Practical operation of exclusion in court, including pre-trial applications, voir dire hearings, consideration of public policy interests, and the consequences of exclusion for the prosecution case.

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. What is the main test the court applies under s.78 PACE 1984 when deciding whether to exclude prosecution evidence?
2. Can evidence obtained in breach of the PACE Codes of Practice be excluded under s.78, even if it is highly relevant to the case?
3. How does s.78 PACE 1984 interact with the right to a fair trial under Article 6 of the European Convention on Human Rights?
4. Give an example of a situation where a confession might be excluded under s.78 but not under s.76 PACE.

Introduction

Section 78 of the Police and Criminal Evidence Act 1984 (PACE) empowers a court to exclude prosecution evidence if, in all the circumstances (including the manner of its acquisition), its admission would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it. The discretion reflects the modern principle that criminal trials must not only deliver justice, but be seen to do so. Issues of fairness run through every stage of criminal process, forming the basis of both the common law and statutory exclusionary frameworks.

Key Term: s.78 PACE 1984
A statutory provision giving courts a broad, discretionary power to exclude any prosecution evidence if, considering all the relevant circumstances, including how the evidence was obtained, its admission would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it.

The provision also supports the right to a fair trial enshrined in Article 6 ECHR and ensures compliance with evolving human rights standards. It thereby acts as a safeguard not only against unreliable evidence, but against evidence obtained in ways that would bring the administration of justice into disrepute.

The Discretionary Power under s.78 PACE 1984

Section 78 PACE 1984 is worded broadly and is central to evidential fairness in criminal trials. It applies to all evidence the prosecution seeks to adduce, regardless of its form—confessional, physical, documentary, identification, or otherwise. If admitting such evidence would undermine the fairness of the proceedings to the extent that the court ought not to admit it, the court may exercise its discretion to exclude it.

Unlike s.76—which relates only to confessions and imposes mandatory exclusion where the statutory criteria are met—s.78 is a discretionary and general exclusionary jurisdiction. The focus is on the effect of admitting the evidence on the fairness of the proceedings as a whole.

Key Term: judicial discretion
The authority of the judge to make certain legal decisions, based on their evaluation of the specific facts and circumstances of the case, rather than being compelled to apply a strict mandatory rule.

Scope of s.78

The breadth of s.78 means it applies beyond confessions to any prosecution evidence, from documentary records to ‘real’ physical exhibits. The most common use is where investigators have breached procedural safeguards, such as PACE Codes, or acted unlawfully, but the discretion remains even where the wrongdoing is less serious, provided the requisite impact on fairness exists.

The evidence may have been obtained:

• Through improper searches or arrests (e.g. without a warrant or without reasonable suspicion);
• By breaching the right to legal advice or to an appropriate adult for vulnerable suspects;
• By failing to follow mandatory identification procedures (e.g. not arranging an identification parade when required by PACE Code D);
• In interviewing suspects in a manner likely to affect reliability or to undermine procedural safeguards or voluntariness;
• As a result of oppressive conduct, overbearing questioning, or inducements.

Events both pre- and post-arrest are within scope, provided the evidence is tendered by the prosecution. Defence and co-defendant evidence are subject only to the common law exclusionary rules (e.g. relevance, prejudice).

Key Term: fairness of the proceedings
The requirement—derived from both domestic law and Article 6 ECHR—that criminal proceedings must be just, impartial, and conducted so the rights of all parties, especially the defendant, are properly protected.

Factors Considered by the Court

When deciding whether to exclude prosecution evidence under s.78, the court will determine:

• The seriousness, nature, and extent of any breach of a legal duty, statutory provision, or code of practice.
• The circumstances of the breach—including whether deliberate, reckless, or inadvertent.
• Whether the breach can be remedied by directions or safeguards short of exclusion.
• The nature and importance of the evidence, and its impact on the overall case.
• The strength of the prosecution’s case apart from the impugned evidence.
• The reliability and probative value of the evidence versus its likely prejudicial impact.
• The effect of admission on the fairness of the trial in the round, not in the abstract.
• Whether exclusion is necessary to protect the reputation of justice or prevent the courts being used as a forum to condone unacceptable official conduct.

The court will weigh these considerations against the public interest in securing the conviction of offenders. In some cases, minor violations will not suffice if the probative value is high and unfairness minor, but serious, deliberate, or flagrant breaches often tip the balance in favour of exclusion.

Key Term: oppression
Any conduct (by police or investigators) that involves torture, inhuman or degrading treatment, physical or psychological violence, or threats thereof; or any other conduct that overbears the will of the subject so as to call into question the reliability or voluntariness of evidence.

Key Term: unreliability
Circumstances that make a confession or other evidence untrustworthy due to the nature, setting, or conditions under which it was obtained (e.g., denial of legal advice, improper inducement, or failure to follow mandatory safeguards).

Relationship with Other Exclusionary Rules

Section 78 is to be considered in the broader context of the exclusionary framework of criminal evidence. While s.78 is general and discretionary, other routes to exclusion include mandatory exclusion under:

• s.76 PACE 1984 (confessions obtained by oppression or in circumstances likely to render them unreliable),
• statutory rules in the Criminal Justice Act 2003 (e.g. for bad character),
• common law rules on relevance and prejudice.

Section 76 requires the exclusion of confessions if the prosecution cannot prove, beyond reasonable doubt, that they were not obtained by oppression or as a consequence of something said or done that renders them unreliable. Where s.76 does not necessitate exclusion—such as for confession evidence not amounting to oppression or unreliability—s.78 remains available to address fairness.

Key Term: voir dire
A ‘trial within a trial’—a hearing (usually without the jury present) to determine the admissibility of disputed evidence, particularly confessions.

Contrastingly, the common law provides that evidence may be excluded where its prejudicial effect outweighs its probative value, or where it is irrelevant to any factual matter in issue. Notably, s.78 has largely supplanted the common law discretion to exclude evidence for unfairness, but the common law still provides the basis for the overall evidential regime and is invoked where s.78 is inapplicable (e.g., in relation to defence evidence).

Human Rights Considerations

Section 78 PACE 1984 is particularly important for ensuring that trial processes comply with the European Convention on Human Rights. The right to a fair trial, protected under Article 6 ECHR, is of the highest importance:

Key Term: Article 6 ECHR
Provides for the right to a fair and public hearing within a reasonable time by an independent and impartial tribunal established by law.

Key Term: Article 8 ECHR
Provides for the right to respect for private and family life, which may be engaged when evidence is obtained by interference with privacy (e.g., surveillance or search).

Where evidence has been obtained in breach of fundamental rights—such as interviewing a suspect who was denied access to legal advice, or searching premises without proper authority—the court, applying s.78, must consider whether admitting it would be incompatible with fairness. Repeated judicial guidance confirms that if the breach causes real prejudice to the ability of the defendant to receive a fair trial or to challenge the evidence, exclusion will often be the proper remedy.

The Human Rights Act 1998 requires UK courts to interpret legislation compatibly with Convention rights, strengthening the imperative to exclude evidence where its admission would make a criminal process unfair. However, the ECHR does not require automatic exclusion of unlawfully obtained evidence (e.g., evidence obtained in breach of Article 8) unless its use would render the trial fundamentally unfair.

Application in Practice

The practical operation of s.78 PACE 1984 has generated a body of case law illustrating its function across a broad range of scenarios, including:

• breaches of the right to legal advice (e.g., denial of a solicitor during police detention or interview, in contravention of s.58 PACE and Article 6 ECHR);
• identification evidence obtained by procedures not compliant with PACE Code D;
• confessions made after oppression or significant breach of procedure (short of those falling directly under s.76 PACE).

The courts will not automatically exclude all unlawfully or improperly obtained evidence. Instead, there is a requirement for the breach to have a significant adverse impact on overall trial fairness. Where the breach is technical or minor and has no substantial bearing on the reliability of the evidence or the ability of the defendant to mount a proper defence, courts are likely to admit the evidence.

Conversely, where the breach undermines essential procedural safeguards, especially those designed to protect vulnerable suspects (such as access to an appropriate adult), or involves bad faith or deliberate disregard for lawful standards, exclusion is more likely. The case law indicates that exclusion is more probable where, for example, police act in cynical disregard of procedural rules, mislead legal representatives, or fail to preserve material that could test reliability.

Worked Example 1.1

A confession is obtained after the police deny the suspect access to legal advice, in breach of PACE Code C. Should the confession be excluded under s.78?

Answer:
The court will consider the nature and significance of the breach, including whether the denial of legal advice was deliberate or inadvertent, how it may have impacted the reliability of the confession, and whether it deprived the suspect of a key safeguard for fairness. If the breach is deemed significant, and the court finds admitting the confession would meaningfully impair trial fairness, the confession may be excluded under s.78, even if not strictly excluded under s.76. The closer the connection between lack of legal advice and the making of admissions, the more likely exclusion will result.

Worked Example 1.2

Police conduct a search without reasonable grounds, contrary to PACE Code A, and find drugs. Can the evidence be excluded under s.78?

Answer:
The seriousness of the breach is decisive. If the search was conducted in bad faith, or involved a flagrant disregard for legal requirements (for example, a lack of reasonable suspicion or deliberate targeting), the court may regard admission of the evidence as condoning improper conduct and exclude it. However, for minor or technical breaches—particularly if the evidence is reliable and there is overwhelming proof of guilt—courts are less likely to exclude the evidence solely on account of procedural breach.

Worked Example 1.3

A witness identification is obtained after police fail to follow Code D procedures. The identification is the main evidence against the defendant. What should the court do?

Answer:
The court will assess whether the failure to follow mandatory identification procedures unfairly affected the reliability of the identification or the ability of the defendant to mount a proper defence. If the breach led to a situation where the reliability of identification evidence cannot be fairly tested or the jury would be deprived of necessary safeguards, exclusion under s.78 may be justified. Conversely, if the breach was minor or did not prejudice trial fairness, the court might allow the identification but issue a suitable warning to the tribunal of fact.

Further Examples of Application

• Admitting evidence from an interview without an appropriate adult for a juvenile: Where police interview a juvenile or vulnerable person in the absence of an appropriate adult, contrary to Code C, and the evidence is significant, courts may exclude it if admitting it would compromise the fairness of the proceedings.
• Admission of evidence after a breach of the right to silence: Where a suspect is not properly cautioned before an interview, resulting in incriminating statements, the court will decide whether this breach risks an unfair trial.
• Evidence obtained by entrapment: While s.78 may be engaged, the court also has a broader power to stay proceedings where prosecution results from conduct that undermines the integrity of the justice system.

Limits and Practical Considerations

Section 78 is not a blanket rule against admission of all unlawfully obtained evidence. The key consideration is the impact on fairness, not the mere presence of a breach. Courts must be vigilant against mere formality, and will not exclude evidence for trivial or technical errors, but significant, substantial, or deliberate breaches are likely to result in exclusion.

Minor failures to follow procedure—where the defendant’s rights are not truly compromised and the evidence itself is convincingly reliable—will generally not lead to exclusion. The closer the nexus between unjust conduct and potential unreliability, the greater the case for exclusion under s.78.

Exam Warning
The discretion under s.78 does not mean that all improperly or unlawfully obtained evidence will be excluded. The test is not strict illegality, but the adverse effect on fairness.

Section 78 also complements, but does not override, other routes to exclusion. For instance, where s.76 applies (confession obtained by oppression or unreliability), exclusion is mandatory. Where s.78 applies (e.g., unfairness short of oppression or unreliability), exclusion is discretionary.

Practical Steps

• Any s.78 application should be raised as early as possible, ideally at a pre-trial hearing, with written submissions if necessary.
• The application is normally determined at a voir dire—in the absence of the jury—so as not to prejudice their fact-finding role.
• If the evidence is excluded and a successful prosecution is no longer possible, a stay of proceedings may result.

Relationship with Entrapment and Abuse of Process

While s.78 can be employed to suppress evidence obtained as a result of police entrapment, courts have stressed that where police conduct is so serious as to make a fair trial impossible, the more appropriate remedy is often a stay of proceedings for abuse of process. Section 78 may still be used where, for example, admission of evidence derived from entrapment would cause such unfairness as to undermine justice, but it is not the sole, nor necessarily the preferred, response.

Summary

Section 78 of PACE 1984 provides an important statutory safeguard to ensure trials remain fair and just. It allows the court, on the application of the defence or its own motion, to exclude prosecution evidence if, in all the circumstances, including the manner of its acquisition, its admission would have a distinctly adverse effect on the fairness of the proceedings. This acts not only to remedy direct unfairness, but to maintain confidence in the justice system, safeguard proper standards of investigation, and give effect to the requirements of Article 6 ECHR. Minor or inadvertent breaches will not usually result in exclusion, but significant or deliberate impropriety that undermines the fairness of proceedings will often justify exclusion.

Key Point Checklist

This article has covered the following key knowledge points:

• The court has discretion under s.78 PACE 1984 to exclude any prosecution evidence if its admission would adversely affect the fairness of the proceedings.
• This discretion is broad, covering all types of prosecution evidence, irrespective of its source or form, provided trial fairness is implicated.
• The seriousness, nature, and circumstances of any breach are critical to the exclusionary decision—deliberate or substantial breaches are more likely to lead to exclusion.
• The public interest in prosecution is balanced with the need for fairness—no automatic exclusion for unlawfulness, but significant or calculated wrongdoing is determinative.
• Section 78 operates alongside other exclusionary rules such as s.76 PACE (confessions) and the common law rules on prejudicial versus probative value, and irrelevance.
• Article 6 ECHR gives added weight to the requirement that evidence should not be admitted if it would make the trial fundamentally unfair.
• Exclusion is not automatic for every procedural breach—minor, technical failures may be disregarded if fairness can be preserved.
• Entrapment and abuse of process are special cases—sometimes requiring a stay rather than s.78 exclusion.
• Applications for exclusion should be made promptly, and are often determined in a voir dire.
• If essential evidence is excluded and the prosecution cannot proceed, the case may be stayed or dismissed.

Key Terms and Concepts

• s.78 PACE 1984
• judicial discretion
• fairness of the proceedings
• oppression
• unreliability
• voir dire
• Article 6 ECHR
• Article 8 ECHR