Below are some examples of the types of assessments Expert Witness Psychiatrists are typically instructed to assess:

1. Fitness to Plead
Psychiatrists evaluate whether the defendant is fit to stand trial, using criteria such as:

Understanding the charges and the court process
Being able to instruct a solicitor
Having capacity to enter a plea and follow proceedings
This is a legal test, but psychiatric evidence is central to the decision.

2. Mental State at the Time of the Offence (MSO)
A crucial part of a psychiatrist’s role is assessing the defendant’s state of mind when the crime was committed, particularly for:

Insanity defence under the M’Naghten rules
Diminished responsibility, often raised in homicide cases
Automatism in rare, extreme cases
These assessments explore whether a mental illness impaired the person’s capacity to understand or control their actions.

3. Diagnosis and Treatment Recommendations
Expert psychiatrists can formally diagnose:

Schizophrenia or psychotic disorders
Bipolar disorder
Severe depression
Personality disorders
Neurodevelopmental disorders (e.g. autism, ADHD)
They can also recommend appropriate treatments, or where applicable, suggest that a hospital order (under the Mental Health Act) is more appropriate than imprisonment.