A lawyer for 32-year-old Neil Hyde told Belfast Crown Court that the Lurgan man had offered the Crown "the very greatest assistance in relation to resolving the notorious killing."
Renowned reporter Martin O'Hagan was shot on September 28, 2001 as he walked home with his wife from a pub in Lurgan. His killing was claimed by the Red Hand Defenders, a cover name used by the LVF at the time.
Hyde has signed a contract under the Serious Organised Crime and Police Act (SOCPA) to become an 'assisting offender' in return for a reduced sentence for 48 LVF-linked offences to which he has already pleaded guilty.
A Crown lawyer said that it was while Hyde was being questioned by detectives from the PSNI's Retrospective Murder Review Unit in September 2008 that he confessed to a number of offences and formally agreed to help police six months later.
Police stood inside and outside the public gallery as around 20 loyalists from the Lurgan area watched in silence as prison officers brought Hyde in handcuffs into the dock at the Laganside court complex.
Hyde, whose address has been given as c/o the Witness Protection Unit, ignored his erstwhile friends and sat quietly as details of his offences were detailed by the prosecution.
In total he has admitted to six charges relating to petrol bombs, nine of affray, drug dealing in cannabis and cocaine, five relating to arson, seven firearms offences, two charges of withholding information in relation to a murder and a wounding.
He's also pleaded guilty to robbery and attempted robbery, aggravated burglary, causing actual bodily harm and managing a meeting in support of the LVF.
All the offences occurred on various dates between January 1, 1992 and January 24, 2008.
Prosecution lawyer Gordon Kerr QC said Hyde had told police he was in a flat on the evening of the murder and named the other people who were present, how a loaded gun was produced and how it later became evident that a shooting was going to take place.
Mr Kerr said Hyde insisted he left the flat unaware of the intended target and took no part whatsoever in the incident.
The lawyer said Hyde also told police what he knew about the murder of another man Graham Edward Marks in Tandragee in April 2001.
At the time police said they believed the killing was linked to a feud between the LVF and the UVF in the area.
Lawyers drew parallels between Hyde's actions in helping police and the decision by brothers Ian and Robert Stewart to testify against alleged UVF men from the Mount Vernon area of Belfast in return for reduced sentences.
Hyde's lawyer said his client had 'crossed the Rubicon' by co-operating with police and put himself and his family in danger for life. He said his decision was the clearest possible indication of his remorse and his determination to turn his back on his previous life.
The lawyer urged Judge Patrick Lynch QC to give Hyde a suspended sentence in return for his promise of the 'highest order of co-operation' with the PSNI.
The judge said he would sentence Hyde next Friday morning.
A man in the public gallery shouted 'You're a liar' at Hyde as he was led away from the court.