## Facts

- The case concerned the application of the diminished responsibility defence under section 2(1) of the Homicide Act 1957 as amended by the Coroners and Justice Act 2009.
- The defence requires proof of a "disruption in mental functioning" from a "recognized medical condition" that significantly impairs the defendant’s abilities.
- Psychiatric analysis was central to establishing the presence and impact of such mental disruption.
- The psychiatric evidence in Brennan was unchallenged by the prosecution.
- The judge was asked to consider if the murder charge should be withdrawn in light of the uncontested evidence.

## Issues

1. Whether unchallenged psychiatric evidence supporting diminished responsibility obligates the judge to withdraw a murder charge in the absence of opposing evidence.
2. How judges and juries should assess the strength and relevance of uncontested expert psychiatric evidence.
3. To what extent defining a "mental disruption" and assessing "significant impairment" are clinical or legal matters.

## Decision

- The Court of Appeal ruled that unchallenged psychiatric evidence which supports diminished responsibility, and is not controverted by other material, requires the judge to withdraw the murder charge.
- The court emphasized that agreed and relevant expert evidence should not be disregarded by juries without clear reasons.
- Judges must assess uncontested expert evidence for clarity, logic, and consistency, and verify its relevance and reliability.
- The ultimate determination of "significant impairment" remains for the jury, even when expert evidence is unchallenged.

## Legal Principles

- Identifying mental disruption is fundamentally a medical (clinical) question best determined by psychiatrists.
- The legal standard for diminished responsibility involves both medical assessment and jury evaluation of impairment.
- Judicial duty includes evaluating the validity and applicability of expert testimony and determining its sufficiency for dismissing the murder charge.
- Juries retain the final decision on whether the legal criteria for diminished responsibility are satisfied, regardless of medical consensus.

## Conclusion

R v Brennan establishes a structured approach to evaluating unchallenged psychiatric evidence in diminished responsibility cases, clarifying the roles of judges, experts, and juries to ensure fair and consistent application of the defence while maintaining ultimate jury authority.


R v Brennan [2014] EWCA Crim 2387