Thursday 29 October 2026Compiled from published reports. Every claim links to its source.

Ireland Crime

Every case followed from the first report to the sentence, or to where the reporting stopped.

Case No. 10283Murder · Co. Donegal · 19 Dec 2023

Donegal man found not guilty of murdering grandfather by reason of insanity

On 19 December 2023 at Carrickcoyle, Derrybeg, Gweedore, Co Donegal, Derek Burns, a 78-year-old man, died from injuries sustained outside his home. His grandson, Derek Mulligan, aged 39, was released from a psychiatric unit in Letterkenny on 18 December, arrested, and admitted the assault in three interviews at Milford Garda Station, and he was charged with murder and four related offences from 17 December 2023. Mulligan pleaded not guilty by reason of insanity to all five counts. On 27 March 2026 a Central Criminal Court jury returned majority not guilty by reason of insanity verdicts on all five counts, and Ms Justice Eileen Creedon committed him to the Central Mental Hospital, with a return date of 31 March 2026 and a psychiatric assessment ordered.

  1. Reportednot reported
  2. Arrestednot reported
  3. Chargednot reported
  4. In court23 Mar
    4 reports
  5. Acquitted27 Mar
    2 reports
  6. Sentenced
reportedhappened, not reportedlatest stagenot yet

Key facts

consolidated from all reports
What happened
Derek Mulligan, aged 39, was charged with murdering his grandfather, Derek Burns, aged 78, outside Burns's home.
Where
The killing took place at Carrickcoyle, Derrybeg, Gweedore, Co Donegal, where Mulligan has an address.
When
  • Sources give the date of the killing as 19 December 2023, and Mr Burns died from his injuries on that date.
  • Other sources say Mr Burns was found unconscious outside his home on 17 December 2023, after his daughter visited at 3.30pm.
Cause
  • Mulligan told gardaí he threw Mr Burns to the ground, repeatedly hit him, and tried to stab him with a pitchfork before using a stone.
  • Two psychiatrists said Mulligan was suffering from paranoid schizophrenia when he killed his grandfather, and the State and defence agreed he had a mental disorder at the time.
Weapon
Mulligan said he struck his grandfather's head with a granite stone and then used a cement block to finish him off.
Investigation
  • Mulligan was released from a psychiatric unit in Letterkenny on 18 December 2023, arrested, and taken to Milford Garda Station.
  • Mulligan was interviewed three times at Milford Garda Station, admitted the assault, and was later detained under section 12 of the Mental Health Act.
Charges
Mulligan pleaded not guilty by reason of insanity to murder and to four related counts from 17 December 2023: criminal damage to a car windscreen, threatening to kill or cause serious harm to Catherine McDermott, and two assaults on Breege McFadden and Derek McFadden at Carrickmacafferty, Derrybeg.
In court
  • The trial took place at the Central Criminal Court before Ms Justice Eileen Creedon and a jury of seven men and five women.
  • On 27 March 2026 the jury returned majority not guilty by reason of insanity verdicts on all five counts after two hours and 22 minutes of deliberation.
Sentence
Mulligan was committed to the Central Mental Hospital, with a return date of 31 March 2026 and a psychiatric assessment by an approved medical officer ordered.
Other details
Mr Burns's daughter found him on the ground, unconscious and bloodied.
77 statements extracted from the articles
  • whatThe accused admits causing fatal injuries to his 78-year-old grandfather. (donegallive.ie)
  • whatDerek Mulligan was found not guilty of murder by reason of insanity by a majority verdict of a Central Criminal Court jury. (rte.ie)
  • whatDerek Mulligan was found not guilty of murder by reason of insanity by a majority verdict. (donegallive.ie)
  • whatMulligan was charged with the murder of his grandfather, Derek Burns, aged 78. (donegallive.ie)
  • whereMr Mulligan is originally from Bunbeg in Co Donegal but had been living in Carrickcoyle. (donegallive.ie)
  • whereThe killing took place at Carrickcoyle, Derrybeg, Gweedore. (donegallive.ie)
  • whereThe killing took place at Carrickcoyle, Derrybeg, Gweedore, Donegal. (donegallive.ie)
  • whereThe killing took place at Carrickcoyle. (donegallive.ie)
  • whereMulligan had an address at Carrickcoyle, Derrybeg, Gweedore, Co Donegal. (donegallive.ie)
  • whenMr Burns died from his injuries two days later on December 19. (donegallive.ie)
  • whenThe killing took place on December 19, 2023. (donegallive.ie)
  • whenThe killing took place on 19 December 2023. (donegallive.ie)
  • whenThe killing of Derek Burns took place at Carrickcoyle on 19 December 2023. (rte.ie)
  • whenMr Burns was found unconscious outside his home on December 17 after his daughter went to visit him at 3.30pm. (donegallive.ie)
  • whenMr Burns died from his injuries on December 19, two days after the attack. (donegallive.ie)
  • causeThe accused said he threw Mr Burns to the ground and repeatedly hit him. (donegallive.ie)
  • causeMulligan admits causing fatal injuries to his grandfather. (donegallive.ie)
  • causeMulligan told professionals that the release from prison of the man who abused him as a child had caused him to spiral. (rte.ie)
  • causePsychiatrists gave evidence that Mulligan was suffering from paranoid schizophrenia when he killed his grandfather. (donegallive.ie)
  • weaponThe accused said he picked up a granite stone and hit his grandfather's head with it. (donegallive.ie)
  • weaponThe accused said he threw a cement block onto his grandfather's head. (donegallive.ie)
  • weaponThe accused said he tried to stab his grandfather with a pitchfork before using the stone. (donegallive.ie)
  • weaponThe accused told gardaí he struck his grandfather's head with a granite stone. (donegallive.ie)
  • weaponThe accused said he used a cement block to finish off his grandfather. (donegallive.ie)
  • weaponMulligan used a granite stone and a cement block to beat his grandfather to death outside his home. (rte.ie)
  • weaponMulligan used a granite stone and a cement block in the attack. (donegallive.ie)
  • investigationMr Mulligan was released from a psychiatric unit in Letterkenny on December 18 and arrested. (donegallive.ie)
  • investigationMr Mulligan was interviewed on three occasions at Milford Garda Station and admitted carrying out the assault on his grandfather. (donegallive.ie)
  • investigationGardaí arrested the accused and interviewed him three times. (donegallive.ie)
  • investigationThe accused admitted assaulting his grandfather and causing the injuries that led to his death. (donegallive.ie)
  • investigationTwo psychiatrists gave evidence that Mulligan was suffering from paranoid schizophrenia when he killed his grandfather, and the jury accepted this evidence. (rte.ie)
  • investigationMulligan was arrested after being released from a psychiatric unit and was taken to Milford Garda Station. (donegallive.ie)
  • investigationMulligan admitted carrying out the assault on his grandfather in interviews with gardaí. (donegallive.ie)
  • chargeDerek Mulligan pleaded not guilty by reason of insanity to the murder of his grandfather Derek Burns at Carrickcoyle on December 19, 2023. (donegallive.ie)
  • chargeMr Mulligan pleaded not guilty by reason of insanity to damaging the windscreen of a Nissan Quashqui belonging to Catherine McDermott. (donegallive.ie)
  • chargeMr Mulligan pleaded not guilty by reason of insanity to threatening to kill or cause serious harm to Catherine McDermott. (donegallive.ie)
  • chargeMr Mulligan pleaded not guilty by reason of insanity to two counts of assaulting Breege McFadden and Derek McFadden at Carrickmacafferty, Derrybeg. (donegallive.ie)
  • chargeDerek Mulligan has pleaded not guilty by reason of insanity to the murder of his grandfather, Derek Burns. (donegallive.ie)
  • chargeThe accused has pleaded not guilty by reason of insanity to threatening Catherine McDermott and damaging her car windscreen on December 17, 2023. (donegallive.ie)
  • chargeThe accused has pleaded not guilty by reason of insanity to two counts of assaulting Breege McFadden and Derek McFadden. (donegallive.ie)
  • chargeThe accused pleaded not guilty by reason of insanity to criminal damage to a car windscreen at Carrickcoyle on 17 December 2023. (donegallive.ie)
  • chargeThe accused pleaded not guilty by reason of insanity to threatening to kill or cause serious harm to Catherine McDermott. (donegallive.ie)
  • chargeThe accused pleaded not guilty by reason of insanity to two counts of assault on Breege McFadden and Derek McFadden at Carrickmacafferty, Derrybeg. (donegallive.ie)
  • chargeMulligan has pleaded not guilty by reason of insanity to murdering his grandfather. (donegallive.ie)
  • chargeMulligan has pleaded not guilty by reason of insanity to damaging a car windscreen on December 17, 2023 at Carrickcoyle. (donegallive.ie)
  • chargeMulligan has pleaded not guilty by reason of insanity to threatening to kill or seriously harm Catherine McDermott. (donegallive.ie)
  • chargeMulligan has pleaded not guilty by reason of insanity to two counts of assaulting Breege McFadden and Derek McFadden at Carrickmacafferty. (donegallive.ie)
  • chargeMulligan was found not guilty by reason of insanity of damaging the windscreen of a Nissan Qashqai belonging to Catherine McDermott on 17 December 2023. (rte.ie)
  • chargeMulligan was found not guilty by reason of insanity of threatening to kill or cause serious harm to Catherine McDermott. (rte.ie)
  • chargeMulligan was found not guilty by reason of insanity of two counts of assaulting Breege McFadden and Derek McFadden at Carrickmacafferty, Co Donegal. (rte.ie)
  • chargeMulligan was found not guilty by reason of insanity of damaging the windscreen of a car belonging to Catherine McDermott on December 17, 2023. (donegallive.ie)
  • chargeMulligan was found not guilty by reason of insanity of making threats to kill Catherine McDermott on the same day. (donegallive.ie)
  • chargeMulligan was found not guilty by reason of insanity of two counts of assaulting Breege McFadden and Derek McFadden at Carrickmacafferty. (donegallive.ie)
  • courtThe defence of insanity applies to all five counts on the indictment. (donegallive.ie)
  • courtMr Mulligan pleaded not guilty by reason of insanity at the start of his trial. (donegallive.ie)
  • courtThe trial continues the next day before Ms Justice Eileen Creedon and a jury of seven men and five women. (donegallive.ie)
  • courtThe case is being heard by a jury at the Central Criminal Court. (donegallive.ie)
  • courtThe trial continues before Ms Justice Eileen Creedon and a jury of seven men and five women. (donegallive.ie)
  • courtThe accused pleaded not guilty by reason of insanity to the murder. (donegallive.ie)
  • courtThe trial is being heard at the Central Criminal Court. (donegallive.ie)
  • courtTwo psychiatrists told the trial that Mulligan was suffering from paranoid schizophrenia at the time. (donegallive.ie)
  • courtThe prosecutor said there is a convergence of psychiatric opinion that Mulligan is entitled to the special verdict. (donegallive.ie)
  • courtThe defence said a humane society seeks to treat rather than punish those who are unwell. (donegallive.ie)
  • courtThe jury is expected to begin deliberations on Friday. (donegallive.ie)
  • courtThe jury of seven men and five women deliberated for two hours and 22 minutes before returning majority verdicts. (rte.ie)
  • courtMulligan is due back before the court on 31 March, and a psychiatric assessment by an approved medical officer has been ordered. (rte.ie)
  • courtThe jury delivered majority verdicts on all five counts of not guilty by reason of insanity after two hours and 22 minutes of deliberation. (donegallive.ie)
  • courtMulligan was committed to the Central Mental Hospital, with his return before the court set for March 31. (donegallive.ie)
  • courtThe judge directed the preparation of a psychiatric assessment by an approved medical officer. (donegallive.ie)
  • sentenceThe judge committed Mulligan to the Central Mental Hospital. (rte.ie)
  • otherThe daughter found her father on the ground, unconscious and bloodied. (donegallive.ie)
  • otherMr Mulligan was later detained by gardai under section 12 of the Mental Health Act. (donegallive.ie)
  • otherPsychiatrists for the State and defence agree that the accused was suffering from a mental disorder when he killed his grandfather. (donegallive.ie)
  • otherBoth psychiatrists agree he was suffering from a mental disorder at the time, enough to bring the insanity defence into play. (donegallive.ie)
  • otherDoctors at Letterkenny Hospital said the injuries were consistent with an assault. (donegallive.ie)
  • otherPsychiatric experts for the State and the defence agree the accused had a mental disorder when he killed his grandfather. (donegallive.ie)
  • otherPsychiatric evidence was given that the accused fulfils the criteria for a special verdict of not guilty by reason of insanity. (donegallive.ie)

The reporting

newest first
  1. 27 Mar2026
    Acquitteddonegallive.ie, first report
    Donegal man found not guilty of murdering grandfather by reason of insanity

    Reports the Central Criminal Court verdict of not guilty by reason of insanity, the order committing Mulligan to the Central Mental Hospital, and the related counts from December 17, 2023.

    accused, Derek Mulligan, 39, male, named, irish (judged from name)Derek Mulliganvictim, Derek Burns, 78, male, non-irish (judged from name)Derek Burnsvictim, Catherine McDermott, female, irish (judged from name)Catherine McDermottvictim, Breege McFadden, female, irish (judged from name)Breege McFaddenvictim, Derek McFadden, male, irish (judged from name)Derek McFadden
  2. 27 Mar2026
    Acquittedrte.ie, follow-up
    Man found not guilty of murder by reason of insanity

    Reports the Central Criminal Court verdict of not guilty by reason of insanity on the murder count and related counts, the committal order to the Central Mental Hospital, and the return date.

    victim, Derek Burns, 78, irish (judged from name)Derek Burnsaccused, Derek Mulligan, 39, male, named, irish (judged from name)Derek Mulligan
  3. 27 Mar2026
    In courtdonegallive.ie, first report
    'Humane society' seeks not to punish those unwell, defence reminds murder trial jury

    Reports the closing speeches in the Central Criminal Court trial. The defence and prosecution both say Mr Mulligan should receive a special verdict of not guilty by reason of insanity. Also lists his related pleas on other counts from the same occasion. No verdict is reported.

    accused, Derek Mulligan, 39, male, named, irish (judged from name)Derek Mulliganvictim, Derek Burns, 78, male, irish (judged from name)Derek Burnsvictim, Catherine McDermott, irish (judged from name)Catherine McDermottvictim, Breege McFadden, irish (judged from name)Breege McFaddenvictim, Derek McFadden, irish (judged from name)Derek McFadden
  4. 26 Mar2026
    In courtdonegallive.ie, first report
    Murder accused told doctors paedophile's release from prison caused him to ‘spiral’

    Trial evidence from two psychiatrists at the Central Criminal Court on the insanity plea. Adds the accused's account of the killing to gardaí, the NGRI pleas to related counts, and the trial's continuation before Ms Justice Eileen Creedon.

    accused, Derek Mulligan, 39, male, named, irish (judged from name)Derek Mulliganvictim, Derek Burns, 78, male, irish (judged from name)Derek Burnsvictim, Catherine McDermott, female, irish (judged from name)Catherine McDermottvictim, Breege McFadden, irish (judged from name)Breege McFaddenvictim, Derek McFadden, irish (judged from name)Derek McFadden
  5. 24 Mar2026
    In courtdonegallive.ie, first report
    Central Criminal Court hears Donegal man "smacked" stone off grandfather's head

    Reports the opening of the Central Criminal Court trial, including the prosecution's account of the accused's interviews, the medical evidence and the related charges against the accused for incidents involving two local families on December 17, 2023.

    accused, Derek Mulligan, 39, male, named, irish (judged from name)Derek Mulliganvictim, Derek Burns, 78, male, irish (judged from name)Derek Burnsvictim, Catherine McDermott, female, irish (judged from name)Catherine McDermottvictim, Breege McFadden, female, irish (judged from name)Breege McFaddenvictim, Derek McFadden, irish (judged from name)Derek McFadden
  6. 23 Mar2026
    In courtdonegallive.ie, first report
    Donegal man (39) pleads not guilty by reason of insanity to murdering grandfather

    Reports the opening of Derek Mulligan's trial, his not guilty by reason of insanity pleas to all counts, and the prosecution's account of his mental state, arrest and interviews.

    accused, Derek Mulligan, 39, male, named, irish (judged from name)Derek Mulliganvictim, Derek Burns, 78, male, irish (judged from name)Derek Burnsvictim, Catherine McDermott, irish (judged from name)Catherine McDermottvictim, Breege McFadden, irish (judged from name)Breege McFaddenvictim, Derek McFadden, irish (judged from name)Derek McFadden