The Police Ombudsman has confirmed that a Crown force informer was a member of a gang that gunned down a father of six in front of his wife and children.
Danny McGurk was shot five times in his Lower Falls home on August 17 2003 in an attack that was blamed on republicans.
Ms McGurk said investigators for the police watchdog, which is examining the circumstances of her brother’s murder, have confirmed the presence of an agent.
Ten arrests were made in the weeks following the shooting but only one person was charged with withholding information -- a charge that was later dropped.
The murder weapon used in the shooting was discovered three months later when the PSNI stopped a car on the Letterkenny Road in County Derry.
Prominent republican John Brady along with a second man and a woman were arrested following the weapons find, charges against all three were later dropped.
Brady, a former IRA prisoner released under the Good Friday Agreement, had his licence revoked following the Derry arrests and is currently in Maghaberry prison.
“The ombudsman confirmed to us that there was an informant in the car and that is the reason we believe that no charges have been brought,” Ms McGurk said.
“Apparently it’s more important to protect the identity of an informer than to catch a gang of murderers.”