Tailored Trial Adaptations for Neurodiverse Defendants: Fitness to Plead and Diminished Responsibility Clarified in De Zoysa v R

Introduction

De Zoysa v R ([2025] EWCA Crim 668) is a landmark Court of Appeal criminal decision, handed down on 23 May 2025 by Dame Victoria Sharp P and fellow judges. It arises from the trial, conviction and sentencing of Louis de Zoysa for the murder of Police Sergeant Matthew Ratana. The case tested fundamental questions about:

• How the ancient Pritchard fitness‐to‐plead criteria apply when a defendant has autism spectrum disorder and acquired brain injury;
• The extent to which trial procedures must be adapted to allow neurodiverse participants to participate fully;
• The availability and scope of diminished responsibility in the context of an “autistic meltdown”;
• Limits on jury site visits and the inalterability of substantive manslaughter law;
• The proper approach to imposing a whole life order for murder of a serving police officer.

De Zoysa, aged 23 at the time of the offence, shot Sergeant Ratana multiple times in a custody cell after having been handcuffed and left unattended in a police van. He was convicted unanimously by a jury, sentenced to life imprisonment with a whole life order, and his appeals against conviction and sentence were refused both by a single judge and by the full Court of Appeal. This commentary examines the court’s reasons and the new legal principles affirmed or clarified.

Summary of the Judgment

The key outcomes of the Court of Appeal’s decision are:

• Leave to appeal against conviction was refused on all three grounds: fitness to stand trial, refusal of a jury view of the holding cell, and alleged misdirection on unlawful act manslaughter permissions.
• The court affirmed that the Pritchard criteria remain the correct test for fitness to plead, and that a defendant need not understand complex legal or medical details to be fit.
• The trial judge’s extensive adaptations (simplified language, visual aids, intermediary) met the requirements of a fair trial for a neurodiverse defendant.
• The refusal to allow the jury to visit the cell was justified: high‐quality 3D imagery and expert/defendant evidence sufficed, and a site visit would not materially improve understanding.
• The court rejected any suggestion that the substantive law of unlawful act manslaughter should be modified to accommodate autism, affirming that only Parliament can change the elements of the offence.
• Leave to appeal against sentence was refused. The court upheld the whole life order for the murder of a police officer, applying the Sentencing Act 2020 and Schedule 21 principles correctly.

Analysis

Precedents Cited

The Court of Appeal relied primarily on:

• R v Pritchard (1836) 7 C&P 303 – the foundational authority establishing the six‐point fitness to plead criteria.
• R v John M [2003] EWCA Crim 3452 – refinement of Pritchard, spelling out the individual capabilities (understanding charges, instructing counsel, giving evidence, etc.).
• R v Marcantio; R v Chitolie [2016] EWCA Crim 14 – further application of Pritchard to modern trials with specialized evidence.
• R v Nica [2021] EWCA Crim 1719 – authority confirming that substantive law on unlawful act manslaughter cannot be judicially adapted for neurodivergent defendants.
• R v Stewart [2023] 1 Cr App R (S) 17 – sentencing guidance on whole life orders and the need to avoid a “tick‐box” approach.

These precedents shaped the court’s conclusions on fitness to plead, jury directions, and sentencing. Importantly, Pritchard’s criteria were applied contextually, recognizing that what a defendant must grasp depends on case complexity.

Legal Reasoning

The court’s reasoning unfolded in several stages:

1. Fitness to plead: The panel reviewed Jeremy Johnson J’s ruling, which had carefully mapped each Pritchard criterion against the evidence of two opposing psychiatrists and an intermediary’s report. Although De Zoysa had autism and brain injury, the judge found he could:
   • Understand the nature of the murder charge;
   • Decide and enter a plea;
   • Instruct counsel;
   • Follow proceedings with simplification;
   • Give evidence coherently with breaks, whiteboard and intermediary support.
   The court held that understanding fine points of diminished responsibility law or nuanced medical details was unnecessary to fitness. A fair trial baseline means the defendant can engage with essential questions, leave complex law to counsel.
2. Jury view application: De Zoysa argued that a visit to the cramped holding cell would help jurors appreciate his sensory experience and borderline meltdown. The judge refused, concluding:
   • High‐definition 3D imagery and video provided more reliable evidence than a subjective visit;
   • Any visceral reaction by jurors to a confined space was irrelevant to legal issues;
   • The disruption, cost and distress outweighed any slight benefit.
   The court endorsed that balancing exercise under CPR Part 39.2(5), confirming that a site visit must materially assist understanding beyond existing evidence.
3. Unlawful act manslaughter directions: On a potential alternative verdict for manslaughter, defence counsel sought a special direction: that jurors consider a dangerous‐act test “through the lens of autism.” The judge rejected this as contrary to settled law. The court affirmed that only Parliament may alter substantive criminal tests; jury directions must state the orthodox test of “objective dangerousness” and “reasonable foresight of harm.”
4. Sentence appeal: The court reviewed the Sentencing Act 2020, section 321(3) and Sched. 21. Murder of a police officer in the line of duty attracts a starting point of a whole life order. The trial judge had addressed:
   • Whether autism diminished culpability – rejected given the deliberate acts over 50 minutes;
   • Aggression, premeditation and public danger of custom‐made ammunition;
   • Mitigation (age, background, brain injury) – partially credited but outweighed;
   • Stewart guidance – judge applied Schedule 21 comprehensively, not mechanically.
   The court found no arguable error in principle or proportionality.

Impact

De Zoysa v R will influence future criminal trials involving neurodiverse defendants by:

• Reaffirming that fitness to plead remains governed by Pritchard, applied flexibly to case complexity, not expanded by partial defences;
• Showing how extensive procedural adaptations—simplified language, intermediaries, visual aids—can constitute a fair trial;
• Confirming that jury site visits may be refused if high‐quality alternative evidence exists and the visit adds no legal value;
• Establishing that substantive offences (manslaughter tests) cannot be modified to suit individual disabilities;
• Underlining that whole life orders for murder of on‐duty police officers remain the norm unless exceptional mitigation is shown.

Complex Concepts Simplified

To aid non‐lawyers, key legal notions unpacked:

• Fitness to plead (Pritchard criteria): A defendant must be able to understand the charge, decide on plea, instruct lawyers, follow the trial and give evidence. It is not required to grasp complex legal tests or medical literature.
• Diminished responsibility: A partial defence to murder. Defendant must show an “abnormality of mental functioning” from a recognized condition that substantially impaired self-control or judgment at the killing moment.
• Autistic meltdown: An intense, involuntary stress response in autism, marked by loss of self-control. It can ground diminished responsibility if it substantially impairs judgment.
• Site visit: When a jury physically visits a crime scene. Judges weigh whether it adds understanding beyond photographs, video or expert evidence, against cost and juror distraction.
• Whole life order: A life sentence with no minimum term. Mandatory for murder of a police or prison officer in the line of duty, unless exceptionally strong mitigation justifies a finite term.

Conclusion

De Zoysa v R crystallizes the modern approach to neurodiverse defendants: fitness to plead remains anchored in Pritchard’s timeless criteria but must be applied in the context of tailored adaptations. The decision confirms that defendants need only sufficient comprehension to engage with core issues—complex legal or scientific detail belongs to their lawyers. It also underscores the judiciary’s careful balancing of procedural fairness (through intermediaries and simplified processes) against practical constraints (refusing site visits when alternative evidence suffices). Finally, the ruling reiterates the inviolability of substantive criminal elements and reaffirms that murder of on-duty officers ordinarily attracts whole life orders.

This judgment will guide trial judges, prosecutors, defence practitioners and legislators in ensuring that neurodiverse and vulnerable defendants are treated fairly without diluting essential legal standards.