Guerin, a crime reporter for the Sunday Independent, was shot dead by assailants on a motorcycle as she was stopped in her car at a traffic light in Dublin. She had been repeatedly targeted for physical attacks, a shooting, and death threats because of her incisive, continuing investigation into Ireland’s criminal underworld that had garnered her CPJ’s 1995 International Press Freedom Award.
Two men, Brian Meehan and Paul Ward, were convicted for her murder in 1999 and 1998. Ward’s conviction was overturned in 2002, but he remains in prison, where he is serving a 12-year sentence for taking part in a prison riot. John Gilligan, a known Dublin drug trafficker, was also charged but was acquitted because of lack of evidence on March 16, 2001, despite the judge’s assertion that there were "grave suspicions" of Gilligan’s complicity in the killing.
On October 23, 2020 Spanish police arrested Gilligan at his villa in Alicante in southeastern Spain as part of an investigation into suspected trafficking of marijuana and prescription drugs from Spain to Ireland and the U.K., the BBC reported. During the raid, police recovered a Colt Python revolver which was buried in the garden of the villa — the same model that was used in the journalist’s murder, The Guardian reported. According to that report, Spanish and Irish police were examining the weapon to determine whether it was used in the assassination.