Limits on Fresh-Evidence Appeals in Joint-Enterprise Murder: Intermediaries, ADHD Evidence, and Diminished Responsibility Where the Defendant Denies the Killing Role

1) Introduction

The appellant was convicted of murder after a joint trial with a co-defendant. The prosecution case was put on joint enterprise: it could not say which man inflicted the fatal stab wound, but alleged both acted together. Following conviction and a life sentence with a minimum term of 25 years (less time served), the appellant sought: (i) extensions of time; (ii) to adduce fresh evidence (psychological/psychiatric and intermediary evidence); and (iii) leave to appeal conviction and sentence.

The appeal raised four conviction grounds (intermediary; diminished responsibility; ADHD/psychological evidence for the jury; and inadequate advice/position regarding giving evidence) and one sentencing ground (manifest excess). The Court of Appeal refused all applications.

2) Summary of the Judgment

The Court also refused extensions of time because there were no arguable grounds of appeal.

3) Analysis

3.1 Precedents Cited and Their Influence

• C v Sevenoaks Youth Court [2009] EWHC 3088 (Admin): Cited for the proposition that a criminal court may direct an intermediary for a defendant via inherent powers. In Richardson, the Court accepted the power exists, but treated its exercise as exceptional and fact-sensitive.
• R v Cox [2012] EWCA Crim 549: Central to the Court’s approach to intermediaries for defendants. Two propositions were deployed: (i) there is no presumption a defendant will have an intermediary even if it might improve the process; and (ii) the court should adapt the trial process to address communication needs. The Court applied those principles to conclude that (a) counsel did what the Practice Direction expects competent advocates to do, and (b) the trial process had already been adapted (not least due to the co-defendant’s vulnerabilities), reducing any marginal benefit.
• R v Erskine and another [2009] EWCA Crim 1425; [2009] 2 Cr App R 29: Relied upon for two linked themes on diminished responsibility: (i) there is no absolute legal requirement for the defendant to admit the killing role before diminished responsibility can be advanced; but (ii) it is ordinarily difficult (save rare cases) to assess substantial impairment without evidence of the defendant’s mental processes at the time. The Court treated Erskine as recognising both legal permissibility and practical evidential difficulty.
• R v Curran [2021] EWCA Crim 1999: Used to reinforce the practical evidential point: substantial impairment typically cannot be sensibly evaluated without evidence of what the defendant was thinking/doing at the relevant time. The Court invoked Curran to explain why, given the appellant’s continuing denial of relevant participation, the diminished responsibility route was not realistically available on appeal.
• R v Sossongo [2021] EWCA Crim 1777: Cited to acknowledge that ASD/ADHD evidence can, in certain circumstances, be relevant to secondary liability for murder. The Court distinguished the present case: there, the defendant testified and the diagnosis emerged post-conviction; here, the appellant did not testify and his case did not present a factual narrative in which ADHD-related processing/communication issues could illuminate intent, knowledge, or agreement for joint enterprise.

3.2 Legal Reasoning

(a) Fresh evidence under section 23 Criminal Appeal Act 1968

The Court structured its approach by reference to s.23(2): capability of belief; whether it may afford a ground for allowing the appeal; admissibility; and a reasonable explanation for non-adduction at trial. The decision shows the Court treating the “may afford a ground” limb as decisive: even credible evidence is excluded if it does not materially engage with safety.

A notable feature is the Court’s firm resolution of disputed factual foundations for the proposed fresh evidence. It found the appellant unreliable on key matters (e.g., frequency of lawyer consultations, alleged inaccuracies in attendance/proof notes), preferred trial counsel’s evidence, and regarded contemporaneous documentation (including prison visit logs and the signed defence statement) as strongly corroborative. Those factual findings then constrained what the expert evidence could achieve on appeal: an opinion resting on mistaken assumptions (notably as to the appellant being the stabber) was treated as undermined.

(b) Intermediaries for defendants: benefit is not the test; necessity and trial fairness are

Applying the then-applicable Criminal Practice Direction (Crim PD 1 2015, General Matters 3F (Intermediaries)), the Court treated “would have benefited” as insufficient. The relevant inquiry was whether the absence of an intermediary impaired effective participation beyond what counsel and ordinary trial management could provide, and whether that impairment impacted the safety of the conviction.

Even though experts considered an intermediary would have helped (e.g., slowing language, using visuals, ensuring breaks), the Court held the trial lawyers had already adapted their communication to the appellant’s needs, and that the appellant’s key choice—whether to give evidence— was made in an informed way. Because the appellant did not testify, the most common “intermediary moment” (facilitating examination-in-chief/cross-examination) never arose.

(c) Diminished responsibility: legally open without admission, but evidentially hard without an account of mental processes

The Court reaffirmed the doctrinal point drawn from R v Erskine and another [2009] EWCA Crim 1425; [2009] 2 Cr App R 29: diminished responsibility does not require an admission of the defendant’s part. However, it treated the appellant’s consistent stance—no animosity, no plan to attack, no knowledge of a knife, no involvement beyond an alleged attempt to help—as practically incompatible with generating the necessary expert foundation for s.2 Homicide Act 1957.

The Court’s handling of the competing psychiatric evidence illustrates a recurrent appellate concern: “substantial impairment” is not a label that can be applied in the abstract. Dr Kareem’s opinion was accepted as methodologically reliable precisely because it acknowledged evidential limits (time lapse, absence of contemporaneous mental state evidence, uncertainty as to the appellant’s state at the material time, and variability of anxiety/depression). Dr Huckle’s diminished responsibility opinion was rejected as internally inconsistent and factually premised on an incorrect understanding of who stabbed the victim.

The Court also emphasised the systemic point from Erskine: allowing a defence not run at trial can “subvert the trial process” absent a persuasive explanation. Here, the Court held trial counsel made a reasonable and proper decision, on the information then available, not to pursue diminished responsibility.

(d) ADHD/psychological evidence for the jury: relevance depends on the live factual issues

The Court accepted the appellant had ADHD (and uneven cognitive indices, including low verbal comprehension with overall average IQ). But it held such evidence would not have assisted the jury because the defence case did not place the appellant’s perception, processing, or judgment under examination in a way that expert evidence could illuminate. Without the appellant’s testimony or a factual narrative linking ADHD symptoms to the disputed mental elements (knowledge, intent, agreement), the evidence risked being generic and non-probative.

(e) Advice on giving evidence and tactical decisions (including non-cross-examination of the co-defendant)

The Court’s reasoning is tightly connected to its factual findings. Having accepted that counsel explained proceedings adequately and that the appellant did not wish to name the co-defendant, it treated (i) the advice not to testify and (ii) the decision not to cross-examine the co-defendant as reasonable forensic judgments. The Court also noted a key practical difficulty: counsel could not put the appellant’s case to the co-defendant (that the co-defendant was present and involved) without breaching the appellant’s instruction not to identify him.

3.3 Impact

• Intermediary applications for defendants: The decision reinforces that “would benefit” is not enough; the appellate question is whether absence undermined effective participation and impacted safety, particularly where experienced counsel can and do implement adaptations without an intermediary.
• Diminished responsibility on appeal: The case sharpens the distinction between legal possibility and evidential practicality. While admission is not required in law, appellate courts will be reluctant to entertain diminished responsibility where the appellant’s own case denies the kind of conduct/mental process evidence needed to assess “substantial impairment” and causative explanation under s.2 Homicide Act 1957.
• Expert evidence discipline: The Court’s rejection of an expert opinion premised on misunderstanding of the appellant’s role underscores the importance of ensuring experts are properly instructed on the prosecution/defence factual alternatives in joint enterprise cases.
• ADHD/ASD evidence: Following R v Sossongo [2021] EWCA Crim 1777, the Court confirms such evidence can be relevant, but only when it bears on concrete issues: how the defendant processed events, formed intention, appreciated risk, or understood participation—typically requiring an evidential platform (often including the defendant’s account).
• Sentencing and neurodevelopmental conditions: The Court signalled that diagnoses alone do not reduce culpability; a demonstrable nexus to the offending and culpability assessment is required, and where the sentencing judge was already aware of the conditions and nonetheless found a leading role, appellate interference will be rare.

4) Complex Concepts Simplified

• Fresh evidence (s.23 Criminal Appeal Act 1968): The Court of Appeal does not automatically consider new material. It asks (among other things) whether the new evidence is believable, whether it could realistically change the safety of the conviction, whether it would have been admissible at trial, and why it was not used then.
• Intermediary for a defendant: A communication specialist who can help a defendant understand questions and proceedings (e.g., simplifying language, pacing, breaks). For defendants, appointment is exceptional: courts prefer adapting the trial process and relying on counsel’s explanations unless fairness requires more.
• Joint enterprise (secondary liability): A route to liability where a person may be convicted of murder if they participated with another in a criminal venture with the requisite mental element (often involving intention/foresight parameters depending on the legal formulation applied at the time). Here, the prosecution alleged both acted together even if the stabber could not be identified.
• Diminished responsibility (s.2 Homicide Act 1957): A partial defence reducing murder to manslaughter if, at the time of killing (or being a party to it), the defendant suffered from an abnormality of mental functioning from a recognised medical condition which substantially impaired certain abilities (understanding conduct, rational judgment, self-control) and explains the killing participation.
• “Substantial impairment”: Not a medical label but a legal threshold, informed by expert evidence. Courts expect expert conclusions to be anchored to evidence of what the defendant was experiencing and deciding at the relevant time.

5) Conclusion

Richardson v R illustrates the Court of Appeal’s insistence on a tight link between (i) proposed fresh evidence and (ii) the safety of the conviction in a joint enterprise murder. The Court reaffirmed that there is no presumption of an intermediary for a defendant and that competent counsel and trial adaptations will often suffice. It also clarified, in practical terms, the limits of raising diminished responsibility on appeal where the appellant’s own case denies the conduct/mental processes needed to prove substantial impairment and explanatory causation under s.2 Homicide Act 1957.

Finally, the decision underscores that neurodevelopmental diagnoses such as ADHD may be forensically significant, but only where they engage with the live factual and mental element issues on the evidence. On the facts found, neither conviction nor sentence was undermined, and all applications (including extensions of time) were refused.