Derek Mulligan found not guilty by reason of insanity in grandfather’s murder

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Derek Mulligan has been found not guilty by reason of insanity of murdering his grandfather, Derek Burns, by a majority verdict of a Central Criminal Court jury. The jury also returned majority verdicts on four other counts: criminal damage to Catherine McDermott’s Nissan Qashqai, making threats to kill or cause serious harm to Ms McDermott, and assaulting Breege McFadden and Derek McFadden.

Mulligan had pleaded not guilty by reason of insanity. The defence said a just and humane society should treat unwell people with specialist care, while Dr Ronan Mullaney said Mulligan could not have known his actions were wrong or refrained from committing them. Prosecution psychiatrist Dr Stephen Monks also said Mulligan was suffering from paranoid schizophrenia when he killed Burns; the judge said both psychiatrists had taken cannabis in Mulligan’s system into account.

Ms Justice Eileen Creedon ordered Mulligan’s commitment to the Central Mental Hospital and directed an approved medical officer’s psychiatric assessment. His return before the court was scheduled for 31 March. The proceedings were reported on 27 March 2026.