FORMER RUC detective Trevor McIlwrath has said that paramilitary groups were so heavily infiltrated by informers and agents near the end of the Troubles that it was almost impossible to make an arrest.
Mr McIlrath has claimed that police investigations at the time were hampered because so many police agents were working within paramilitary groups.
"You couldn't catch anybody any more because everybody was an agent," he said.
"When you read de Silva (report) and you see they are numbered as L20, L21, L22, L28... Right up to L 30 and L40.
"We know the names and every single one of them are working for the branch."
He also believes security force collusion was rife at the time.
"It was widespread in every terrorist group," he said.
"And it stops at the door of the state and they are ultimately responsible. (Look at) Stakeknife, you have one part of the state looking for him and you have the other half hiding him."
The former CID officer and his partner Johnston Brown were both arrested and questioned in 2006 by then Police Ombudsman office officials as part of their probe into the UVF murder of Raymond McCord Jr in 1997. Both men felt they were being penalised for speaking out about what was going on within the RUC.
The ex-policeman said the years since Pat Finucane's murder have been personally difficult and claims he received threats in the past which he believed came from Special Branch.
"I hope to get peace inside my head because I am a mess with nightmares, murders, mayhem. I wake about eight or nine times a night, I am taking 40 tablets a day to survive. I am still an outpatient at Holywell hospital because I told the truth," he said.
"All I want is peace to be able to be left alone...I have had the PSNI, the RUC, the ombudsman, the Garda Síochána coming to my door accusing me of things that I did not do."
Retired RUC Detective Superintendent Alan Simpson said Special Branch agents within paramilitary groups were badly handled.
"They could have used all those agents to play one against the other and demolish the terrorist unit. Instead they kept recruiting and recruiting and recruiting and recruiting, like a stamp collector, what’s the point?"
Mr Simpson added that the RUC had a disjointed approach.
"We weren't going forward as one force," he said. "We were going forward as a force within a force. The whole thing could have been so different if they had played a straight hand, an honest hand."
