Post‑Trial ADHD Diagnosis as Fresh Evidence: “Functional Effective Participation” Governs Safety Under s.23 Criminal Appeal Act 1968

Case: Pilley, R. v [2026] EWCA Crim 384
Court: England and Wales Court of Appeal (Criminal Division)
Date: 25 February 2026

1. Introduction

This application concerned whether convictions following a seven-month fraud trial were unsafe because, at the time of trial, the defendant’s neurodevelopmental condition (Attention Deficit Hyperactivity Disorder, “ADHD”) and alleged cognitive impairment were undiagnosed and therefore not accommodated or explained to the jury.

The applicant, Andrew James Pilley, had been convicted at Preston Crown Court of two counts of fraudulent trading (Companies Act 2006, s.993), one count of being concerned in an arrangement facilitating criminal property (Proceeds of Crime Act 2002, s.328), and one count of fraud by misrepresentation (Fraud Act 2006, ss.1–2). He was sentenced to 13 years’ imprisonment. He sought an extension of time and leave to appeal, relying primarily on fresh psychological evidence said to bear on his ability to prepare for trial, instruct lawyers, and give evidence fairly.

A prior ground relating to alleged jury irregularity had already been refused by a differently constituted Court of Appeal; this judgment deals solely with the “fresh evidence / neurodiversity” ground.

Key issues

  • Whether fresh expert evidence of ADHD and cognitive weakness should be received under s.23 Criminal Appeal Act 1968.
  • Whether the absence of diagnosis and trial adjustments rendered the trial unfair and the convictions unsafe.
  • How to assess “effective participation” where the defendant functioned extensively in complex real-world and trial settings.

2. Summary of the Judgment

The Court refused the extension of time and refused leave to appeal. It also declined to receive the fresh psychological evidence because, even taking the evidence broadly at its highest in the applicant’s favour, it did not provide any ground for allowing the appeal: the convictions were safe.

The Court accepted that (i) the applicant had ADHD and (ii) his intellectual functioning was below average in certain respects. However, it concluded that he had participated effectively in the proceedings: he gave detailed evidence over 18 days, engaged with extensive documentation, was represented by experienced lawyers who raised no contemporaneous concern about his capacity to participate, and the case against him depended heavily on documentary and recorded evidence rather than mere impressions of demeanour.

3. Analysis

3.1 Precedents Cited

R v Pendleton [2001] UKHL 66

The Court relied on R v Pendleton [2001] UKHL 66 for the central proposition that the ultimate appellate question remains whether the conviction is unsafe, even where the appeal is framed as one based on fresh evidence. Fresh evidence does not create a separate, free-standing route to success; it is assessed by reference to safety.

R v Pabon [2018] EWCA Crim 420

The Court also cited R v Pabon [2018] EWCA Crim 420 (at [60]–[64]) to reinforce the same controlling test: the Court’s function is not to conduct a re-trial or to decide how it would have run the case with hindsight, but to determine whether the conviction is unsafe in light of the new material.

Practical effect of the cited authorities in this case: they anchored the analysis to safety, prevented the inquiry from becoming “trial management by hindsight,” and framed s.23 as a discretionary gateway rather than an entitlement.

3.2 Legal Reasoning

(a) The s.23 framework and “de bene esse” approach

The Court set out s.23 Criminal Appeal Act 1968, including the statutory considerations in s.23(2): credibility, potential to afford a ground of appeal, admissibility, and explanation for not adducing it at trial. Consistently with common appellate practice, the Court examined the expert material de bene esse—i.e., provisionally—so as to decide whether it should be received at all.

Crucially, the Court’s conclusion that the convictions were safe meant the evidence could not “afford any ground for allowing the appeal,” so it declined to receive it.

(b) Neurodiversity is relevant, but not determinative

The Court recognised contemporary understanding that neurodevelopmental conditions (including ADHD and “other forms of neurodiversity”) can impede effective participation and may require early identification and tailored adjustments (referencing the Equal Treatment Bench Book and the developing jurisprudence on vulnerable defendants). But it treated this as a contextual principle, not a presumption of unfairness:

  • ADHD (or cognitive difficulty) does not of itself mean a defendant cannot participate effectively.
  • The absence of adjustments does not necessarily mean the trial was unfair.
  • The question is fact-specific: whether, “viewed in the round,” the defendant could understand proceedings, instruct lawyers, and present the defence.

(c) “Functional impact” assessed against real-world and trial performance

The Court’s central evaluative move was to test the clinical opinions against abundant evidence of functioning:

  • At trial: the applicant gave extensive evidence over 18 days, had a long examination-in-chief supported by document files, and could engage with complex material. Judicial interventions were characterised as facilitating clarity, not unfair pressure.
  • In the case evidence: the prosecution relied on extensive documents and recordings; verdicts were not depicted as turning solely on demeanour.
  • In life and work: the applicant had founded and managed substantial businesses employing many staff, operated in demanding commercial environments, and handled lengthy PACE interviews—evidence the Court regarded as materially informative about capacity to cope with complexity.

This “functional impact” focus also drove the Court’s response to the expert dispute: it preferred Professor Young’s expertise on ADHD but cautioned against treating psychometrics as determinative in isolation from real-world performance.

(d) Caution about retrospective accounts from trial counsel

The Court accepted trial counsel’s sincere view that a known diagnosis might have changed preparation, advice on giving evidence, and applications for adjustments. However, it warned against the natural distortions of hindsight in retrospective professional assessments—especially where new information emerges post-conviction.

The Court also considered the counterfactual: if the applicant had not testified, the jury would have been left largely with interviews under caution, limited defence evidence, and an expert report; the jury would have been directed about adverse inferences under section 35 of the CJPOA 1994, which the Court regarded as potentially “compelling” in this case given the centrality of the applicant’s state of mind.

(e) Expert evidence: qualification, methodology, and remit

Although the Court ultimately did not need to resolve every technical dispute, it made several points of wider forensic significance:

  • Clinical competence matters: the Court found it “unsatisfactory” for an expert to critique another’s clinical assessment while being unable to undertake an independent clinical assessment themselves, particularly where severity and diagnosis are disputed.
  • Validity testing disputes: the respondent’s expert relied on Performance Validity Tests (PVTs) to suggest malingering/invalid performance; the applicant’s expert accepted some validity failures can occur for non-malingering reasons (fatigue, anxiety, mistrust, etc.).
  • Experts must not decide the appeal: the Court noted criticism that one report strayed into telling the Court that non-expert evidence “would in itself” be sufficient to dismiss the appeal. While the Court treated this as illustrating the correct *approach* (holistic assessment), it implicitly reaffirmed the boundary between expert opinion and the judicial determination of safety.

(f) The “unsafe conviction” conclusion

Even assuming significant ADHD symptoms and some below-average intellectual functioning, the Court was not persuaded that the applicant was unable to participate effectively or that realistic trial adaptations would have altered the trial’s course. It noted, in particular:

  • No issue of unfitness to plead or lack of capacity to stand trial.
  • No contemporaneous concern from experienced defence lawyers about ability to instruct or testify.
  • Transcripts demonstrated detailed, articulate engagement (even if sometimes expansive/argumentative).
  • Count 4 (internet forum campaign) evidenced dishonest conduct not dependent on “detail in business” arguments and could legitimately affect the jury’s assessment of credibility across counts.

3.3 Impact

(a) Fresh evidence appeals based on late ADHD/neurodiversity diagnoses

The judgment reinforces a practical threshold: a post-trial diagnosis is not, without more, a route to quashing convictions. The applicant must show a material functional impact on effective participation (and thus fairness) sufficient to render the conviction unsafe. This is likely to influence how future applicants frame such appeals: not merely “diagnosis unknown,” but “diagnosis unknown plus demonstrated impairment at trial producing identifiable unfairness.”

(b) Holistic evidential evaluation

The Court placed weight on “real world” functioning (commercial management, PACE interviews, trial engagement) alongside clinical testing. Future litigation may increasingly involve:

  • close transcript-based analysis of evidence-giving performance;
  • contemporaneous observations by legal teams;
  • functional history (employment, business, communications) to contextualise psychometrics.

(c) Expert evidence standards in neurodiversity contexts

Although not cast as a new rule, the Court’s critique of an expert opining on disputed clinical matters without clinical qualification to assess is a warning sign for instructing parties: appellate courts may scrutinise not only conclusions, but whether the expert is practically able to perform the evaluative tasks their opinion presupposes.

(d) Trial management and adaptations

The Court acknowledged modern guidance promoting adaptations (breaks, pacing, intermediary use, tailored directions). The judgment may therefore be cited both ways:

  • by defendants, to emphasise the importance of early identification and potential adjustments; and
  • by prosecutors/respondents, to argue that absence of adjustments does not equate to unfairness where functional participation is demonstrated.

4. Complex Concepts Simplified

  • s.23 Criminal Appeal Act 1968 (fresh evidence): allows the Court of Appeal to admit new evidence not used at trial if it is necessary/expedient in the interests of justice. The Court considers credibility, relevance to allowing the appeal, admissibility, and why it wasn’t called earlier.
  • “Unsafe” conviction: the appellate standard in criminal cases; the court asks whether it can be confident the conviction is sound, considering the whole case (including new material if admitted).
  • De bene esse: the court looks at the new material provisionally to decide whether to admit it; it does not mean it has already been accepted as evidence.
  • Effective participation: the defendant’s ability to understand proceedings, follow evidence, instruct lawyers, and give their account fairly. Neurodiversity may affect this, but it is evaluated in context.
  • PVTs (Performance Validity Tests): tests used to check whether a person’s performance on cognitive tests is reliable (e.g., whether poor performance might reflect non-engagement or exaggeration). Disputes often arise about what “failures” mean.
  • WAIS-IV: a standard IQ and cognitive profile test. Scores can indicate strengths/weaknesses in specific domains, but courts may be cautious about treating them as determinative without functional context.
  • DSM-5: diagnostic criteria manual used in clinical practice (including ADHD criteria).
  • Section 35 CJPOA 1994: permits a jury (with judicial direction) to draw adverse inferences where a defendant does not give evidence at trial.

5. Conclusion

Pilley, R. v [2026] EWCA Crim 384 confirms that late-emerging ADHD/neurodevelopmental diagnoses will only assist on appeal if they translate into demonstrated unfairness affecting effective participation and thereby the safety of the conviction. Applying the safety-focused approach in R v Pendleton [2001] UKHL 66 and R v Pabon [2018] EWCA Crim 420, the Court treated neurodiversity as an important lens but not a presumption of injustice. The decisive emphasis was on functional participation evidenced by transcripts, contemporaneous professional observations, and sustained real-world performance. On that holistic view, the Court found the convictions safe and refused both admission of the proposed evidence and leave to appeal.