5.4 Discretionary Exclusion of Unfair Evidence
Key Takeaways
- Section 78(1) of PACE 1984 confers a broad statutory discretion on the court to exclude prosecution evidence if its admission would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it.
- Section 78 applies exclusively to evidence on which the prosecution proposes to rely; it cannot be used by the prosecution to exclude defence evidence or by one co-defendant against another.
- Breaches of the PACE Codes of Practice (especially Code C governing detention and questioning) must be 'significant and substantial' to trigger exclusion under section 78 (R v Walsh).
- Unjustified denial of access to legal advice under section 58 of PACE 1984 is a grave procedural breach that frequently results in the exclusion of subsequent interview evidence under section 78 (R v Samuel).
- In undercover police operations, entrapment does not constitute a substantive defence under English law, but evidence obtained by state agents who actively induce or instigate crime will be excluded under section 78 or lead to a stay of proceedings (R v Looseley).
5.4 Discretionary Exclusion of Unfair Evidence
While section 76 of the Police and Criminal Evidence Act 1984 (PACE 1984) provides for the mandatory exclusion of improper confessions, Section 78 of PACE 1984 provides a general, discretionary safeguard against the admission of any unfair evidence tendered by the prosecution. Section 78 is the primary legal mechanism used by criminal practitioners to challenge prosecution evidence obtained through procedural impropriety, police misconduct, or unlawful investigative techniques.
1. Statutory Threshold under PACE 1984 Section 78(1)
Section 78(1) of PACE 1984 provides:
"In any proceedings the court may refuse to allow evidence on which the prosecution proposes to rely to be given 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."
Key Features of Section 78:
- Exclusively Prosecution Evidence: Section 78 applies solely to "evidence on which the prosecution proposes to rely." It cannot be invoked to exclude evidence tendered by a defendant or co-defendant (R v King [1983] 1 WLR 411).
- Broad Applicability: Unlike section 76 (which applies only to confessions), section 78 applies to all forms of prosecution evidence, including confessions, identification evidence, search and seizure disclosures, cell-site data, breathalyzer results, and undercover surveillance evidence.
- Focus on Trial Fairness: The statutory test is whether admitting the evidence would have "such an adverse effect on the fairness of the proceedings that the court ought not to admit it." The court's focus is on protecting the integrity of the judicial process, not merely punishing police misbehaviour.
2. PACE Codes of Practice & The 'Significant and Substantial' Test
Police investigations are governed by statutory Codes of Practice issued under section 66 of PACE 1984, most notably Code C (Detention, Treatment and Questioning of Persons by Police Officers) and Code D (Identification Procedures).
The Significance Test: R v Walsh
Not every technical breach of PACE or its Codes of Practice results in the exclusion of evidence under section 78. In R v Walsh (1989) 91 Cr App R 161, the Court of Appeal established that to justify exclusion under section 78, breaches of the Codes of Practice must be "significant and substantial".
Common Code Breaches Triggering Exclusion:
- Failure to Record Interviews Verbatim: Paragraph 11.7 of Code C requires contemporaneous or audio-recorded logs of all suspect interviews. Off-the-record conversations or unrecorded "informal chats" in police vehicles prior to formal interview routinely lead to exclusion under section 78 (R v Canale [1990] 2 QB 637).
- Failure to Caution: Questioning a suspect without administering the statutory caution required by Code C para 10.1.
- Interrogation After Refusal of Legal Advice: Continuing to question a suspect after they have requested legal counsel, before counsel arrives.
- Breaches of Rest and Refreshment Requirements: Conducting interviews during mandatory continuous rest periods guaranteed by Code C para 12.2.
3. Denial of Access to Legal Advice: Section 58 PACE
Under Section 58(1) of PACE 1984, a person arrested and held in custody at a police station is entitled, if he so requests, to consult a solicitor privately at any time.
Delaying Legal Advice under Section 58(8)
Access to legal advice may only be delayed in indictable offences where an officer of at least the rank of Superintendent authorizes delay on specific statutory grounds set out in section 58(8):
- That exercise of the right will lead to interference with or harm to evidence connected with an indictable offence.
- That exercise of the right will lead to alerting other suspects not yet arrested.
- That exercise of the right will hinder the recovery of property obtained as a result of such an offence.
Strict Judicial Scrutiny: R v Samuel
In R v Samuel [1988] QB 615, the Court of Appeal emphasized that the right to legal advice is a fundamental constitutional right. Superintendent authorizations to delay access must be supported by specific, objective evidence rather than generalized suspicion. If police unlawfully delay access to a solicitor, any confession obtained during the period of unlawful delay will almost invariably be excluded under section 78.
4. Undercover Operations, Entrapment & R v Looseley
English criminal law does not recognize entrapment as a substantive defence to criminal liability. A defendant cannot plead "I was entrapped" to secure an acquittal. Instead, entrapment is addressed procedurally under section 78 or via an application to stay proceedings as an abuse of process.
The Leading Authority: R v Looseley
In the landmark House of Lords decision in R v Looseley [2001] UKHL 53 (and its companion European Court authority Teixeira de Castro v Portugal (1998) 28 EHRR 101), the court established the distinction between legitimate undercover policing and impermissible entrapment:
| Investigative Category | Police Conduct Parameters | Legal Outcome under s.78 / Abuse |
|---|---|---|
| Unvarnished Opportunity | Officers provide an unvarnished opportunity for a suspect to commit an offence, acting as an ordinary customer in an existing illegal market. | Evidence Admissible: Legitimate undercover surveillance; trial remains fair. |
| Active Inducement / Incitement | Officers initiate contact, use persistent pressure, financial bribery, emotional manipulation, or trickery to entice a person with no pre-existing disposition into committing a crime. | Evidence Excluded / Stayed: Impermissible entrapment; violates Article 6 ECHR; proceedings stayed or evidence excluded under s.78. |
Judicial Test for Entrapment under Looseley:
- Did the police cause the commission of an offence that would not otherwise have been committed?
- Did the officers act as passive investigators or active instigators?
- What was the nature of any inducement, threat, or exploitation of vulnerability?
5. Preservation of Common Law Discretion: Section 82(3)
Section 82(3) of PACE 1984 explicitly provides:
"Nothing in this Part of this Act shall prejudice any power of a court to exclude evidence (whether by preventing the question from being put or otherwise) at its discretion."
This provision preserves the historical common law power established in R v Sang [1980] AC 402, permitting judges to exclude prosecution evidence where its prejudicial effect outweighs its probative value. While section 78 has largely superseded Sang in practice due to its broader fairness mandate, section 82(3) remains a vital statutory safety net.
Summary of Discretionary Exclusion Principles
| Mechanism | Scope / Trigger | Key Precedent | Practical Effect |
|---|---|---|---|
| Section 78(1) PACE | All prosecution evidence where admission adversely impacts trial fairness. | R v Walsh [1989] | Discretionary exclusion of evidence (confessions, searches, Code breaches). |
| Code C Breaches | Failure to observe detention, interview, and recording rules. | R v Canale [1990] | Significant & substantial breaches lead to s.78 exclusion of interview logs. |
| Denial of s.58 Right | Unlawful delay of access to legal advice. | R v Samuel [1988] | High threshold to justify delay; breach almost always excludes confessions under s.78. |
| Entrapment / Undercover | State agents actively enticing or pressuring crime. | R v Looseley [2001] | Distinction between presenting opportunity (admissible) vs active inducement (excluded/stayed). |
| Section 82(3) PACE | Preservation of common law discretion (Sang). | R v Sang [1980] | Excludes evidence where prejudicial effect outweighs probative value. |
During a police station detention following an arrest for robbery, investigating officers refuse a suspect's request to consult a solicitor under section 58 of PACE 1984, claiming informally that 'lawyers slow down interviews.' Officers then conduct an unrecorded 45-minute interview in an interview room during which the suspect makes admissions. At trial, defence counsel applies under section 78 of PACE 1984 to exclude the interview evidence. How should the trial judge rule?
Undercover police officers suspect that a defendant may be involved in illicit drug supply. An undercover officer contacts the defendant repeatedly over three weeks, offering large sums of money, making threats of physical harm, and appealing to personal sympathy until the defendant eventually agrees to source a single package of cocaine for the officer. The defendant had no prior criminal record for drug offences. At trial, defence counsel applies under section 78 of PACE 1984 to exclude the undercover officer's evidence on the ground of entrapment. Applying R v Looseley [2001] UKHL 53, how should the court resolve the application?
At a Crown Court trial for burglary, the prosecution seeks to adduce a blood-stained glove recovered from the crime scene. The defence applies to exclude the glove under section 78 of PACE 1984, arguing that police officers seized the glove without completing a formal search log at the scene. How should the trial judge evaluate this section 78 application?