A terminally ill dissident will spend his final years in prison after being convicted of killing two British soldiers in Northern Ireland but another high-profile republican was cleared of the murder.

Cystic fibrosis sufferer Brian Shivers, 46, was handed a life sentence after a judge found him guilty of being part of the gang that gunned down Sappers Patrick Azimkar, 21 and Mark Quinsey, 23, outside Massereene Army barracks in Antrim on March 7, 2009.

Just months before unemployed divorcee Shivers, from Magherafelt, Co Londonderry, took part in the killings, a doctor told him he had only three or four years to live.

His co-accused, high-profile republican Colin Duffy, from Lurgan, Co Armagh, was acquitted of the charges in the non-jury trial at Antrim Crown Court by Mr Justice Anthony Hart.

It was the third time in the last two decades that 44-year-old Duffy has walked free after being charged with murdering security force members.

There were angry scenes outside the court yesterday as the republican emerged, with loyalist demonstrators hurling vitriolic abuse at him.

Earlier, relatives of the two sappers wept openly in court as he was acquitted. But the room fell silent an hour later when Justice Hart delivered the guilty verdict for Shivers.

After the verdicts, Sapper Quinsey's sister Jaime said they had got a measure of justice.

"Mark and Patrick were murdered as a result of a vicious cowardly act within hours of going to serve their country in Afghanistan," she said.

"After nearly three years of heartache we have come a little bit close to justice."

Sapper Azimkar's mother Geraldine added: "This was a terrible crime which stole Patrick and Mark's young lives from them.

"Losing Patrick has devastated our family and has forever cast a dark shadow over our lives."

Police vowed that the investigation into the Massereene attack would go on.

"We will continue to pursue all of those involved in these evil murders," said Police Service of Northern Ireland Chief Super-intendent Peter Farrar.

The English soldiers, from the 38 Engineer Regiment, were about to begin a tour of duty in Afghanistan when they were gunned down in an attack by republicans opposed to the Good Friday peace deal of 1998. Sapper Quinsey, from Birmingham, and Sapper Azimkar, from London, were dressed in their desert fatigues and were within hours of leaving the base.

They were collecting pizzas at the front gate when they came under fire. Two other soldiers and two pizza delivery drivers, were injured in the gun attack.

DNA on matchsticks found in the partially burned-out Vauxhall Cavalier getaway car used in the ambush and abandoned eight miles away proved Shivers's undoing.

Duffy was cleared even though the judge said DNA evidence found on the tip of a glove linked him to the getaway car.

Justice Hart said: "There must be strong suspicion that Duffy did know what was going to happen and that that is why he has refused to give evidence.

"However, suspicion, no matter how strong, is not sufficient by itself to establish guilt beyond reasonable doubt, and is not an acceptable substitute for facts from which guilt can be properly proved."