Structuring Instructions for a Single Joint Forensic Psychiatric Expert

The Procedural Role of the Single Joint Expert

In criminal proceedings, the court may exercise its case management powers to direct the appointment of a single joint expert. This is designed to ensure the efficient resolution of complex psychiatric issues. While CrimPR Part 19 governs the instruction of experts generally, the appointment of a single joint expert requires clear, proportionate, and focused instructions from each defendant who shares the expert. An expert’s overriding duty is to the court, and this duty remains paramount regardless of whether the instruction is unilateral or joint. Effective instructions allow the psychiatrist to address specific legal questions without being subsumed in extraneous clinical history.

Defining the Scope of Inquiry

When drafting instructions for a single joint expert, clarity regarding the primary legal question is essential. In cases of contested mental capacity, this often requires the psychiatrist to address the relevant legal tests applied by the criminal courts, such as the criteria for fitness to plead and stand trial. Instructing parties should avoid broad requests for a generic mental health report. Instead, questions should be narrowly tailored to the specific legal test, such as whether a mental disorder or impairment of mental functioning renders the defendant unable to participate effectively in the trial process.

Forensic practitioners typically require access to comprehensive medical records, including GP notes, secondary care mental health records, and prison healthcare files. Instructions should explicitly authorise the expert to review these materials, as reliance on self-report alone necessitates appropriate caveats regarding symptom validity. Where the question of malingering or the exaggeration of psychiatric symptoms is relevant to the instruction, parties may ask the expert to consider the use of validated psychometric tools. If an intellectual disability is suspected, specific instruction regarding the necessity of a WAIS-IV assessment for baseline cognitive capacity should be discussed.

Distinguishing Clinical Diagnosis from Legal Responsibility

A frequent difficulty in joint instructions is the failure to distinguish between the presence of a mental disorder and the impact of that disorder on criminal culpability. Expert psychiatric opinion should assist the court by evaluating whether a condition, such as PTSD or a personality disorder, reaches the threshold of “substantial impairment” required for a plea of diminished responsibility under the Homicide Act 1957. Instructions should ask the expert to address the three limbs of diminished responsibility: the ability to understand the nature of conduct, form a rational judgement, and exercise self-control.

Solicitors must ensure that the expert is asked to differentiate between symptoms arising from a diagnosable psychiatric disorder and those attributable to acute drug or alcohol intoxication at the time of the offence. The latter is generally distinct from an underlying mental health condition. In cases involving potential Mental Health Act 1983 disposals, the expert may be directed to consider the feasibility of a Section 37 hospital order, or a hybrid order under Section 45A, provided there is sufficient evidence regarding current treatment needs and criteria for secure hospital admission.

Practical Considerations for Drafting Questions

To assist the expert in preparing a report that addresses the requirements of the court, the following elements should be integrated into the letter of instruction:

• Identify the specific legal questions (e.g., fitness to plead, diminished responsibility, or sentencing mitigation).
• Specify the documentation provided for review and request that the expert notify the parties if critical evidence appears to be missing.
• Request a clear distinction between factual history provided by the defendant and information corroborated by independent records.
• Direct the expert to consider relevant, established risk assessment frameworks where future dangerousness is a factor in sentencing.
• Require the expert to state whether their opinion is contingent upon the accuracy of specific, disputed facts provided in the case papers.

The instructing solicitor should be mindful that the expert must remain independent. It is not the role of the expert to advocate for the defence or prosecution, nor to negotiate the findings. If the single joint expert determines that they lack the necessary information to provide a firm opinion on a core issue, they should be encouraged to state this limitation clearly in their report, rather than offering an opinion that is not supported by the available evidence.

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