Mary Evans with a photo of her son Gerard

A dig for the remains of Gerard Evans, a south Armagh man killed and secretly buried by the IRA, is due to begin in bogland in Co Louth tomorrow following information given to the Sunday Tribune.

A member of the IRA's south Armagh brigade came forward to this newspaper in January with details of Evans' murder and a map of where he said the victim was buried. That information was passed onto the Independent Commission for the Location of Victims Remains.

Evans (24) was last seen alive in March 1979 as he hitched a lift home from a dance in Castleblaney. The IRA leadership, supported by Sinn Féin, has long denied involvement in his disappearance but the south Armagh brigade member said they were lying.

Work to locate Evans' body will begin tomorrow on the farmland two miles from Hackballscross. Diggers have already been moved onto the site and drainage systems have been put in. However, the heavy rain is expected to make excavation work a long and painstaking process. Geophysical tests have been carried out and cadaver dogs were also brought in.

Evans' mother Mary (76) said: "I'm hopeful they'll find Gerard but I don't want to get my hopes up too high because I've seen so many other families disappointed over the years. The commission has done great preparation at the site and I'm praying they'll be successful."

The search is expected to last for a considerable time. It took 18 months for the body of Danny McIlhone, another of the Disappeared, to be found in Co Wicklow. Weather and other conditions meant the dig had to be halted several times.

The masked member of the south Armagh brigade who met the Sunday Tribune admitted to being part of the 12-strong team that killed Evans.

"We held him for three days. He confessed very quickly to being an informer. He wasn't tortured. He pleaded for mercy. He pleaded not to be killed, and then he said his prayers. He was shot once in the back of the head." It is the first time anyone involved in a disappearance has spoken to the media.

The IRA has admitted disappearing nine people during the Troubles, but has long denied responsibility for Evans.

"People who stand shoulder-to-shoulder with Gerry Adams when he comes to south Armagh know the IRA killed Gerry Evans. There's no political reason to keep lying. Just let Mrs Evans give her son a Christian burial before she dies. Put that family out of its misery," the IRA man said.

Mary Evans has said she doesn't want "recrimination or revenge" for her son's murder: "All I want is to bring him home."

The IRA man defended the killing and secret burial but said there was no reason why, 15 years into the peace process, the IRA leadership still refused to tell the truth.