Psychiatrist Expert Witness — How They Assist Across UK Courts (Adult)

What psychiatrists do
Consultant psychiatrists provide independent, clinically-grounded opinions on diagnosis, capacity, risk, causation and prognosis. Their overriding duty is to the court, not the instructing party, and expert evidence must comply with the relevant procedural codes (CPR Part 35; CrimPR Part 19; FPR Part 25). Reports include methodology, reasoned opinions and a compliant statement of truth/declarations.

Criminal courts (Magistrates’ & Crown Court)
Common questions include fitness to plead/stand trial, insanity and diminished responsibility, participation measures, risk and disposal options (e.g., Mental Health Act hospital/restriction orders). A psychiatrist assesses diagnosis, cognitive abilities and each limb of the Pritchard test; if unfit, the court proceeds under the Criminal Procedure (Insanity) Act (including a trial of facts). Opinions also inform sentencing and treatment pathways; experts must remain objective under CrimPR r.19.2.

Civil courts (County Court & High Court)
Psychiatrists opine on primary/secondary psychiatric injury (e.g., PTSD, depression), causation and apportionment, litigation capacity, prognosis, treatment and functional impact (work and daily living). Expert evidence is limited to what is reasonably required; courts may direct single joint instruction and experts’ meetings/joint statements. Reports and conduct must follow CPR 35 and PD 35 (independence, balance, consideration of contrary facts, and clear reasoning).

Family courts (FPR Part 25)
Adult psychiatrists are instructed where a parent’s mental illness may affect parenting capacity, safeguarding risk and welfare planning. The court’s permission is required and expert evidence is restricted to what is necessary; directions set the questions, timescales and attendance. Reports must comply with PD 25B (duties, report content, statement of truth) and remain strictly impartial.

Coroners’ courts (Inquests)
Psychiatrists assist with causation and prevention in deaths involving mental disorder (e.g., suicide), reviewing care pathways, risk assessment and system issues. Coroners have a wide discretion whether to call expert evidence and will do so where it assists with the statutory questions.

Immigration & Asylum Tribunal (FtT/UT IAC)
Experts diagnose trauma-related and other disorders (e.g., PTSD, major depression, psychosis), evaluate credibility impacts, assess suicide/self-harm risk, and advise on fitness to give evidence, detention and removal risks. The current Tribunal Practice Direction (1 Nov 2024) emphasises independence, clarity, and focused evidence and signposts the Equal Treatment Bench Book and vulnerable-witness guidance; separate presidential guidance covers litigation friendswhere capacity to conduct proceedings is in doubt.

Fitness to plead / fitness to stand trial — summary
Question: Can the defendant participate effectively now? Psychiatrists evaluate understanding of proceedings, ability to instruct lawyers, comprehend evidence and engage with the process (the Pritchard criteria). If unfit, the judge may order a trial of facts under the Criminal Procedure (Insanity) Act; recommendations should also address adjustments that might restore fitness.

What to provide on instruction
Letter of instruction with specific questions tied to the legal test; full medical/mental-health records; witness statements; custody/detention records (if relevant); chronology; and any prior reports. Ask the expert to state assumptions, limitations and any further information required to reach a safer conclusion, consistent with the procedural codes above.