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Man To Serve Life Without Parole For Role In Marshfield Murder, Burglary

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Contact: Beth Stone: 508-584-8120

PLYMOUTH – A man has been sentenced to State Prison after a jury convicted him on murder, burglary, and firearms charges in connection with the death of a Marshfield man, Plymouth County District Attorney Timothy J. Cruz announced today.

Today, after a two-week trial, a jury deliberated two hours before finding Mark C. O’Brien (DOB: 11/28/75) of South Boston, guilty of one count each of Murder, Aggravated Burglary, Unarmed Robbery, and five counts each of Larceny of a Firearm and Unlawful Possession of a Firearm. Plymouth Superior Court Judge Jeffrey A. Locke sentenced O’Brien to serve Life in state prison without the possibility of parole on the Murder charge, 15-30 years in state prison on the Aggravated Burglary and Unarmed Robbery charges, and four to five years in state prison on the Larceny of a Firearm charges. Those sentences are to run concurrent. Judge Locke sentenced O’Brien to serve two years in state prison on the five counts of Unlawful Possession of a Firearm, which was deemed time served.

On September 16, 2015, Marshfield Police received a 911 call reporting the death of 45-year-old Robert McKenna, who was discovered in his home at 190 Damon’s Point Road by a friend. McKenna was pronounced dead at the scene and his body was taken to the Office of the Chief Medical Examiner for autopsy, where the Medical Examiner ruled the death a homicide and identified the cause of death to be exsanguination due to injuries to McKenna’s right arm that severed large blood vessels and lacerations of the head.

The case was prosecuted by Deputy First Assistant District Attorney Christine Kiggen and Assistant District Attorney Jessica Elumba, along with Assistant District Attorneys Nathaniel Kennedy and Kathleen Kramer. The case was investigated by State Police Detectives assigned to the Plymouth County District Attorney’s Office, Marshfield Police, State Police Crime Scene Services, the State Police Crime Lab, State Police Search and Rescue Team, State Police K-9 Officers and the State Police Collision Analysis and Reconstruction Team.

September 30, 2019