A loyalist paramilitary group calling itself the Red Hand Defenders claimed responsibility for the murder.
Allegations that the British state security forces were involved in her killing led to a public inquiry.
It found no evidence that state forces directly facilitated her murder, but could not exclude the possibility that individual members had helped the perpetrators.
It said that the Royal Ulster Constabulary (RUC) failed to protect her and that she had been publicly threatened and assaulted by officers, which helped legitimize her as a target.