New RTÉ series highlights brutal treatment of innocent men by Garda 'Heavy Gang'

Una Lynskey was aged just 19 when she went missing near her home in Ratoath in October 1971 and her body was later found in the Dublin mountains.

Three young local men, Martin Conmey, Dick Donnelly and Martin ('Marty') Kerrigan all signed what they claimed were forced confessions admitting to the abduction and killing, which led to another brutal murder.

"We just happened to be in the area at the same time more or less," Martin Conmey (70) tells the Sunday World.

"There was a car seen by several witnesses. A strange car with a middle-aged man and we were only kids at the time. They never even bothered to look up that, that was the annoying thing."

Martin suspects they were singled out by investigating gardaí because they were driving a Zepher car similar to the one reported.

"I was only 20. Marty Kerrigan was only 19. Dick Donnelly was 22. We were only kids. I had never stepped foot in a police station before in my life," recalls Martin.

The trio were brought in on a Monday night for questioning in Trim garda station and were given no food or rest until they were released on the Wednesday night.

"Myself and Marty signed confessions, but purely under duress," explains Martin. "It was step by step, the guards were kind of nearly putting words in our mouths, kind of leading questions.

"We were beaten badly. My friend Dick, Lord of mercy on him, got a serious doing, with a poker. I seen the wounds on him myself on his back."

Martin served three years in prison until his case was overturned and declared a miscarriage of justice. He never got an apology from gardai, but received compensation from the State.

Dick Donnelly, who never signed a confession and who died last year, was found guilty and served several months before an appeal found in his favour.

But Marty Kerrigan never got to see justice as he was brutally killed by two of Una Lynskey's brothers and her cousin.

They were later handed down sentences of three years for manslaughter.

"When Marty's life was taken I don't think they are going to try say 'we're sorry', that they took the life of an innocent man. It would be a hard pill for them to swallow," Martin points out.

"I knew Una well; a lovely girl, really nice. I knew them all, we used to pal around together.

"They obviously believed the guards and were fed information by the guards. The whole thing was desperate, the way it was handled."

The Lynskey case is one of a trio looked at by the RTÉ programme, including the infamous Sallins train robbery involving Nicky Kelly, and the Kerry Babies case, which centred on Joanne Hayes.

Ann Donnelly was married to Dick Donnelly and was also Marty Kerrigan's sister. She got to know Dick better due to his link with her brother during their ordeal and fell in love with him. She believes the trio were targeted purely because they had been on the same road that night.

"Later on that night when they were coming back down the road with Martin, there was guards on the road and they stopped to see what was happening," she says.

"They were told Una was missing. They went out looking for her like everybody else, but because they were on the road and they told the guards they saw this other car, but the guards obviously never believed there was another car and a lot of people seen the other car, not just Marty and Dick."

She says her family home was meant to have garda protection because of threats.

"There was a guard outside our house every day, every night... He picked Marty up in Ratoath and asked him where he was going and Marty said he was going to a dance in Kilmoon, which was a few miles further on.

"They stopped a little bit further down at the graveyard and the guard went into a house and left my brother in the car.

"The Lynskeys and John Gaughan came along and pulled Marty out of the car," she adds.

Her brother's death was absolutely horrific.

"He was tortured. He was dead before they tried to castrate him. How they got away with manslaughter and they going around with a knife. "

Gerry O'Carroll was a Detective Garda Sergeant for over 35 years and for five of them was in the 'Murder Squad'.

"One of the reasons I took part in the programme was to deny that and heard it was going to be kind of hostile," he tells us. Now retired, he maintains there was no violence used by him or his colleagues.

"I never saw anyone been beaten, as true as God, I don't know what they are talking about. Interrogation is tough, hard, grilling, I didn't spare it. As I said before it's no tea party. But I never lifted a finger nor saw anyone doing it to anyone."

Crimes and Confessions, RTÉ ONE Monday 9.35pm