Courts / Dublin / Report

'Monster' Derek Boyd gets life for murder, with sentence for killing sister referred back to circuit court

Date
2026-07-28

Stage
Sentence

Primary locality
Dublin

County
Dublin

Summary

Derek Boyd, 31, was sentenced to life imprisonment at the Central Criminal Court for the murder of Mark Carroll, 34, at a north Dublin home on June 9, 2024. The jury unanimously rejected the defence of self-defence, finding Boyd guilty after a trial where he had pleaded not guilty. Justice Melanie Greally described the killing as senseless and motiveless, noting Boyd was serving the suspended portion of a prior manslaughter sentence for his sister's death when the offence occurred. The court ordered that Boyd's suspended sentence for the 2022 manslaughter be referred back to the Circuit Court for re-entry. The State entered a nolle prosequi on a separate charge of assault causing harm against Boyd. Chantelle Harcourt, 34, who pleaded not guilty to impeding Boyd's prosecution, remains subject to that charge; the jury recorded a disagreement on the related counts, meaning the matter was not concluded. The victim's family described Boyd as a monster in an emotional impact statement. Boyd's sentence dates from August 5, 2025.

Who, what, where, when and why

What: Report matter: 'Monster' Derek Boyd gets life for murder, with sentence for killing sister referred back to circuit court. Charges or matters: impeding her partner's prosecution and it was the State's case that she knew some or all of what had occurred that night and avoided telling the truth to gardai in the hours after the fatal stabbing; murdering Mr Carroll (34) at his home on June 9, 2024; assault causing harm to his girlfriend Ms Rock in her home, where gardai noted on arrival that she was bruised, bloody-faced and visibly shaking. Procedural stage: sentence

When:

March 2022 Hearing Or Sentence
August 5 2025 Hearing Or Sentence
June 9, 2024 Hearing Or Sentence
March 19, 2022 Incident
March 21, 2022 Incident
2026-07-28 Publication

Case subjects

Chantelle Harcourt

Defendant

Charges: impeding her partner's prosecution and it was the State's case that she knew some or all of what had occurred that night and avoided telling the truth to gardai in the hours after the fatal stabbing (Alleged Or Contested)

Plea: Not guilty

Derek Boyd

Background Person

Charges: murdering Mr Carroll (34) at his home on June 9, 2024; assault causing harm to his girlfriend Ms Rock in her home, where gardai noted on arrival that she was bruised, bloody-faced and visibly shaking; impeding her partner's prosecution and it was the State's case that she knew some or all of what had occurred that night and avoided telling the truth to gardai in the hours after the fatal stabbing (Alleged Or Contested)

Plea: Not guilty

Outcome: Derek Boyd has been jailed for life for murdering a father-of-four at his north Dublin home and told that his sentence for the manslaughter of his sister four years ago will now be referred back to the Circuit Court. Boyd (31), who was serving the suspended part of his sentence for killing his sister when he fatally stabbed father-of-four Mark Carroll in the chest, was today described by the victim's family as a "monster".