Each Day in Newry Eamon Collins sees neighbours he knows are IRA members, some of whom he "betrayed". And some days he passes people in the town whose relatives he was responsible for murdering.

Eamon Collins lives with his wife and four children in a working-class district of Newry. Tricolours fly in the area and republican graffiti are daubed on the walls. More than 10 years ago the IRA ordered him out of the town, but he returned eventually, without the threat against him being officially lifted.

He could live elsewhere, but it seems to be part of Collins's almost masochistic way of dealing with his past. "I am part of this community," he says.

He is a small man, aged 43, intelligent and articulate, and with a large ego. He is one of that odd group of former IRA members, such as Sean O'Callaghan and Martin McGartland, who have recently broken the republican rule of omerta and written about their experiences.

But he has confronted his period as an IRA member in a more self-searching manner than the other ex-IRA men. "I am not a converted terrorist. I am someone who has to work with this all the time." He concedes he is also a "mess of contradictions", almost simultaneously confronting and recoiling from his past.

Several people, possibly 15 or even more, were murdered because of his actions as an IRA intelligence officer in the first half of the 1980s. But then, in 1985, he cracked under interrogation and turned supergrass. Twelve people faced serious terrorist charges, including six murders, as a result of his statements. Eventually he recanted and they were released.

Collins himself was charged with five murders, but because the judge believed his original confessions were induced as "a result of inhuman and degrading treatment", he too was freed. "I beat the rap," he says.

He has written a book, Killing Rage, which will become a vital reference, providing a rare and stark insight into the modus operandi of IRA members.

Collins himself appears to inhabit a dark, internal world. There's some of the horror Conrad wrote about in The Heart of Darkness. His home is dominated by six large, troubling, macabre black-and-white paintings by the Belfast artist Rita Duffy of death, suffering, and turmoil. "There's great truth in her work," he says.

While he feels remorse for his actions, there are also confusion and contradiction in his comments and, at times, residual justification for his acts. "There's no way that I can psychologically dump what I was and say `that's an end to it'. But there is no ambiguity in my commitment to peace now."

What Collins has achieved in Killing Rage is to de-romanticise any possible notions that IRA, or any other republican or loyalist paramilitary, activity is a noble or patriotic pursuit.

A work like Martin Dillon's Shankill Butchers opened a little light into why so many loyalist killings involve prolonged torture, barbarity and crude sectarianism. It's not the sole territory of loyalism by any means, but it is more a feature of loyalist than republican actions.

Collins in his book deals with the flip, but equally chilling, side of the same dirty coin. Here we have the cold, methodical planning for death; the careful surveillance of an intended victim's movements; the picking of a choice venue for the murder; the actual killing; and the follow-up operations to spirit the killers safely away from the murder zone.

Such calculation entailed an enormous hardening of the heart. In order to set up his victims, Collins had to see them with their children, with their wives, going to church, having a drink, meeting their friends, doing their daily rounds.

Some of the book is extremely hard to read. He describes how as a customs officer he worked with Ivan Toombs, a part-time UDR major, of how he met his children, and how in the two years he knew him he constantly schemed ways to have him killed, and of how he eventually succeeded. Collins doesn't hold back. He describes a child crying "Daddy, Daddy, Daddy", as his father is gunned down.

Again he talks of an elderly offduty policeman having a drink in a bar and seeing his killers approaching. "No boys, not me," he pleads at the moment of impending death. He describes a blindfolded informer suspect thinking he has been cleared but, unknown to him, getting the thumbs down from an IRA kangaroo court.

There's much more of this almost casual brutality in the book. It's relentless and absolutely credible. And yet he can still lament that he never had a chance to apologise to his erstwhile comrades. "I betrayed them and I was wrong."

And with equal contradiction he adds: "If peace prevails, in maybe 10 or 15 years from now, people who carried out the most horrendous, merciless acts will have dirges written about them. History will be sanitised and they will be heroes, but I don't want any part of that. There was nothing heroic about this war."

What Collins and his comrades in the Newry area did, hundreds of other republican and loyalist paramilitaries did throughout Northern Ireland with the same breathtaking vanity and arrogance. From the localised picture created by Collins, it takes little imagination to draw the bigger picture of how most killings were executed in the same mundane, merciless way. Collins himself talks of the "horrific banality" of murder.

Collins was a Marxist. He says that his ideology, and issues like unionist discrimination, inequality, RUC brutality and British army humiliation of his parents were partly instrumental in his joining the IRA.

But he also concedes he may have been drawn to the IRA originally as much for atavistic sectarian reasons. He recalls a recent "painful" row he had with a relative: "She said something about bigotry, adding that I wasn't a bigot. And I said, `Well, of course, I am a bigot in some senses of the word'.

"And she said `But you were never reared like that'. And I said `Who are you kidding? Of course, I was raised as a bigot. Wasn't I told all about the priests' heads being stuck out on Creggan graveyard, and the Famine, and everything else?' Jesus Christ, didn't I get it all? And, of course, to an extent I do it myself to my own children."

He gets agitated when asked if he accepts that his actions were evil. "I don't know whether there is evil. All I know is this: that all those operations were very hard for me to cope with. My conscience would not let them rest. It was when I eventually had no conscience as regards a murder that I began to collapse. Now, I don't think that is the mind of anybody who is evil," he says.

And he protests: "I don't believe there is evil in me. Seriously there's not, there's not, no, definitely not."

Collins says that he has always had a conscience. He admires some IRA members who he believes were courageous and principled, but despises others for their callousness. He describes how and why he finally broke with the IRA, much of which was down to self-loathing, and loathing of some of the IRA members operating in the Dundalk and Newry areas.

"I began to see certain contradictions in us as human beings. I said to myself: who gives me the right to stand in judgment of people? Is it history? Is it my past? Is it what I learnt at my mother's knee?

"I was always aware of what I was doing, and I carried the pain and burden of that for many years. I suppose it concerned me when I saw others not feeling the same way. And I don't know what that is. Is that being a good soldier or is it being evil? I don't know. I honestly can't answer that?"

After a long interview with him, he is still hard to figure out, probably because there are a lot of things he hasn't yet figured himself, or are too traumatic to confront. He adverts to how the idea of a military uniform, even an imaginary one, cushions people, whether British soldier, UVF or UDA or IRA member, from seriously thinking what the business of killing is really about.

"We have to be soldiers, because how else can we take the life of another human being?"

Collins admits that he hasn't fully come to terms with his past actions. "But I've come a long way, and I'm still working on it." He adds that hundreds of other paramilitaries, without his introspective facility, will face emotional turmoil and trauma if this peace succeeds.

"That's why I think a South African-type truth commission would be a great idea. People will have to come to terms with their pasts, in so far as they can, and such an initiative would be a tremendous help."

He knows that truth is a difficult journey, for Collins himself hasn't yet fully faced up to his own past, despite all the self-analysis. He is a man who seeks to reconcile two irreconcilable desires, who is trying to achieve the impossible. "I am trying to be sensitive and apologetic to my victims, and to the people who have suffered because of my betrayal," he says.