The Supreme Court has dismissed an appeal by Joseph Heffernan, upholding the requirement that a person relying on diminished responsibility must prove the defence on the balance of probabilities.
The appeal concerned the interpretation of section 6(2) of the Criminal Law (Insanity) Act 2006. Heffernan argued that the defence should have to raise only a reasonable doubt about his liability for murder. The Court held that the prosecution must still prove the unlawful killing and the intent required for murder beyond reasonable doubt. Diminished responsibility is a separate, mitigatory defence that reduces the consequence of a proven murder to manslaughter.
Heffernan was convicted of murdering Eoin Ryan after a nine-day trial in 2013. The parties agreed that Heffernan unlawfully caused Ryan’s death in Cappabeg, Barefield, Ennis, on 7 June 2011. The trial issues included intent, insanity and diminished responsibility. Heffernan told gardaí that he had killed a man and described believing the devil was involved. A prosecution psychologist said he appeared delusional when assessed at the garda station. A prosecution psychiatrist later said Heffernan had a mental disorder, but in her opinion it did not substantially diminish his responsibility; she considered the killing explicable by intoxication.
The defence did not call evidence at trial. The jury was directed to consider diminished responsibility and intoxication. The trial judge rejected the defence request for a reasonable-doubt standard and directed that diminished responsibility had to be proved on the balance of probabilities. The jury convicted Heffernan of murder, and the Court of Appeal dismissed his appeal.
In the Supreme Court, the prosecution’s burden to prove the elements of murder remained unchanged. The Court said the diminished-responsibility defence did not require the accused to disprove an element of the offence. It also noted the practical difficulty for the prosecution of proving that a person’s responsibility was not diminished by mental disorder, particularly where assessment requires expert evidence and an accused cannot be compelled to undergo a medical examination.
The Court concluded that the statutory wording, including “establish”, placed a persuasive burden on the defence. It held that the trial judge correctly directed the jury and dismissed the appeal. The Court’s ruling addressed the burden and standard of proof; it did not alter Heffernan’s murder conviction.