“Reasonable Lines of Inquiry” Re-affirmed: The Court of Appeal Clarifies Prosecution and Defence Duties in Child-Sex Cases – A Commentary on BTC, R. v ([2025] EWCA Crim 902)

Introduction

In BTC, R. v the Court of Appeal (Criminal Division) revisited the perennial question of when failures of investigation, disclosure, or defence advocacy render a conviction unsafe. The appellant (“BTC”) had been convicted of sexually touching his 8-year-old son (“C”). He appealed on two broad fronts: (1) the Crown and/or defence had neglected to explore material about the child’s watching pornography, covering his eyes during TV sex scenes and expressions of affection towards his father; and (2) the defence had not developed a “motive to fabricate” case against the child’s mother (“M”), resting on historic domestic acrimony and an allegedly malicious letter to the Home Office.

Lord Justice Warby, delivering the judgment of the court on 24 June 2025, dismissed the appeal. In doing so the Court crystallised and re-emphasised doctrinal boundaries concerning:

• the scope of the prosecution’s duty to pursue “reasonable lines of inquiry” under the Criminal Procedure and Investigations Act 1996 (CPIA);
• the restrictive gateway of s.41 Youth Justice and Criminal Evidence Act 1999 (YJCEA) when the defence seeks to cross-examine a child complainant on sexual matters;
• the stringent test for overturning convictions based on alleged forensic or tactical errors by trial counsel (R v Clinton, “all the promptings of reason and good sense” standard).

While the Court did not purport to create new law, its structured restatement of these principles — especially the proportionality aspect of the CPIA duty — will likely serve as a leading authority whenever similar disclosure / investigation arguments arise, particularly in child-sex prosecutions where digital devices are involved.

Summary of the Judgment

The Court granted an extension of time and leave but ultimately upheld the conviction, holding:

1. No prosecution breach. The police’s decision not to seize or forensically interrogate the child’s iPad, after the child casually mentioned solitary pornography viewing, was within the bounds of “reasonable lines of inquiry”. The point was disclosed to the defence, satisfying the CPIA.
2. No advocacy incompetence. Defence decisions not to seek leave under s.41 YJCEA for cross-examination about pornography, nor to pursue old social-services records, nor to deploy the historic Home Office letter, were legitimate tactical choices. They did not meet the high threshold for “demonstrable incompetence” as required by R v Clinton and R v Day.
3. No real possibility of a different verdict. Even had the unexplored avenues been pursued, there was no realistic prospect the jury would have acquitted.

Analysis

3.1 Precedents Cited

• Kelly (Richard) [2015] EWCA Crim 500 – two-stage test for non-disclosure appeals.
• R (Ebrahim) v Feltham Magistrates’ Court [2001] 1 WLR 1293 – proportionality limit on investigative duty.
• R v Clinton [1993] 1 WLR 1181 – standard for appellate intervention based on counsel errors.
• R v Day [2003] EWCA Crim 1060 – need for incompetence plus unsafe outcome.
• Ben-Rejab [2011] EWCA Crim 1136 – watching pornography as “sexual behaviour” under s.41.
• R v LT [2024] NICA 64 – Northern Irish authority where child’s clandestine pornography viewing justified defence questioning.

The Court distinguished R v LT as fact-specific and refused to treat it as a new, general principle compelling inquiry into a complainant’s exposure to pornography.

3.2 Legal Reasoning

1. CPIA “Reasonable Lines of Inquiry”. Drawing on para 3.5 of the CPIA Code of Practice and Ebrahim, the Court held that reasonableness is context-sensitive and subject to proportionality. Once C denied the father had shown him pornography and admitted isolated, self-initiated searches, further device examination would have been “speculative”.
2. Section 41 YJCEA Gateway. The defence would have faced a “high threshold” to obtain leave to question C about pornography because such questioning must bear directly on a “relevant issue” and its exclusion must risk rendering the verdict unsafe. The Court doubted this could be met given (i) vagueness of C’s admission; (ii) lack of nexus to the specific “gear-stick” touching allegation.
3. Advocacy Competence Test. Adopting Clinton, the Court stressed it will not “second-guess” tactical decisions unless they fly in the face of “reason and good sense”. Here, counsel reasonably avoided lines that might (a) prejudice the jury against a permissive parent whose child watches porn, (b) open damaging character evidence, and (c) undermine an unblemished character direction.
4. Safety Assessment. Even assuming lapses, the Court found no “real possibility” of an acquittal had the additional topics been pursued (Kelly test).

3.3 Potential Impact

The judgment is poised to influence future litigation in three intersecting domains:

• Digital-device enquiries in sex cases. Defence arguments that the Crown must forensically examine every device referenced by a complainant are unlikely to succeed unless clear, case-specific relevance is shown.
• Section 41 applications involving child access to pornography. BTC underscores that such evidence will seldom pass the statutory gateway unless it plausibly explains how the specific allegation arose. Mere exposure to sexual material is insufficient.
• Post-conviction challenges based on counsel “failures”. The Court’s robust endorsement of counsel’s tactical latitude offers persuasive armour for future respondents resisting “hindsight” appeals.

Complex Concepts Simplified

• CPIA Duty to Investigate & Disclose: Police must follow up reasonable leads and share relevant material. They are not obliged to chase every speculative possibility.
• s.41 YJCEA “Sexual Behaviour” Bar: Defence cannot ask complainants about their sexual conduct (including solitary pornography viewing) unless the judge gives leave, satisfied that excluding the evidence might make the trial unfair.
• “Unsafe” Conviction Test: An appeal court quashes a conviction only if there is a real possibility the jury would have decided differently absent the complained-of error.
• Advocacy Incompetence Standard (Clinton): The bar is high: the tactical decision must be plainly unreasonable and must have caused an unfair or unsafe outcome.

Conclusion

BTC, R. v is more than a case-specific dismissal; it is a lucid reaffirmation of limits on investigative and disclosure duties, the stringency of the s.41 YJCEA gateway, and the respect accorded to trial counsel’s tactical autonomy. The Court’s proportionality-centred approach signals that criminal justice will not be derailed by speculative enquiries, nor by retrospective dissatisfaction with strategic choices that were reasonable at the time. Practitioners should therefore:

• Frame CPIA arguments around clear, non-speculative relevance;
• Prepare concrete, causally linked grounds when seeking s.41 leave;
• Document tactical decisions contemporaneously to withstand appellate scrutiny.

Ultimately, BTC serves the broader legal landscape by reconciling the rights of the accused, the complainant’s statutory protections, and the practical realities of criminal investigation, thereby reinforcing confidence in verdicts where those boundaries are respected.