Paul Blackburn spent 25 years in jail for a crime he didn't commit. Now at 45 he's still getting to grips with a world he last experienced as a teenager

Four years after his conviction was quashed, six years after he was released from prison on licence and a full 31 years since he was first arrested for a brutal crime which it is now abundantly clear he did not commit, Paul Blackburn has barely even begun to impose some sort of order on his life.

"It's only been a few months now since I've had my own house. Before that I just flitted from place to place to place," says Blackburn, now a lean, crop-haired 45-year-old with greying stubble. "I've lived on sofas on floors, lived on the streets, lived in tents. Anything, anywhere, just not to stand still.

"I couldn't stand still. I was too afraid. Too afraid of what might happen if I stood still as I thought I would end up killing myself. That was the biggest worry when I got out of prison, that there would be nobody left to fight, and I'd just commit suicide, that it was the fight which was keeping me going.

"I still have nightmares. I wake up and there's a person-sized pool of sweat on the bedsheets."

Blackburn was just 15 when, in 1978, he was jailed for life for the attempted murder and sexual assault of a younger boy. That he served a quarter of a century in jail – or rather being shuttled between 18 different jails – was due to his refusal to acknowledge any guilt. He similarly declined the protection commonly given to sexual offenders, and so endured regular beatings.

In March 2003, two years before the appeal court formally reversed his conviction, in the process labelling the two Cheshire police officers who led the case as perjurers, Blackburn was permitted to leave prison. He was offered almost no support on how to re-enter a complex, baffling world he had last experienced as a teenager.

"I'd been locked up since I was 15 years old. I'm now getting out at the age of 40. Never mind the movie, I was a 40-year-old virgin. It was scary shit for me. And there was nobody there to help me. My probation officer was decent in her way but she was embarrassed to speak to me about some things."

Self-educated, charismatic and fiercely articulate, Blackburn has forged something of a post-prison role addressing academics and professional conferences about his experiences, and what can be learned from them.

But any initial impression of composed self-assuredness is deeply misleading. Beset since he left jail by intermittent drug and alcohol abuse, an inability to form lasting relationships and what he calls "a serious, serious problem" of contemplating suicide, Blackburn's ordeal moulded him into a mass of contradictions.

Inured by years of prison confrontation against any concern for his physical safety – "I can be in whatever nasty area of London at 4am surrounded by drug addicts, crackheads and robbers, it holds no fear for me. I've just been living with them all for 25 years" – he finds visiting supermarkets utterly terrifying. "It was a big Asda, I turned round and walked out again. It's all just too much for me. Too much information, too much choice, too much going on."

Similarly, while he is easy company, utterly open in discussing the emotional, even sexual, impact of his time in jail with someone he has met only a couple of hours before, Blackburn remains fundamentally a loner, whose friends and girlfriends are wearily used to waking up to find he has departed and is now hundreds of miles away, having driven restlessly through the night.

"For 25 years I pretty much lived totally within my own head," he says. "My emotions have been cut off completely pretty much my whole life. To open up to another person and be open – I didn't know how to do it."

This mental disquiet is not helped by the fact that, notwithstanding the appeal court ruling in May 2005, there has been almost no official acknowledgement of the injustice he suffered. He still awaits any significant sum in compensation, while neither the Home Office, which as late as 1996 refused him leave to appeal, nor Cheshire police have expressed regret.

"There has never been anything official, and there never, ever will be," Blackburn says. "So far we've had one letter back from the [Cheshire police] which basically says: 'Tough shit, fuck off. We're admitting nothing and we never will.'"

Such conduct is particularly galling given that the evidence which sent Blackburn to jail for his entire adolescence and young adulthood appears, in retrospect, so pitifully thin.

What has never been in dispute is that a terrible crime took place on 25 June 1978. A nine-year-old boy, fishing on waste ground by a canal in Warrington, Cheshire, was snatched by a knife-wielding teenager and led to a disused sewage works. There, he was sexually assaulted, beaten, stabbed and left for dead under a wooden board weighed down with bricks. He was found 28 hours later only after neighbours carrying out a last, frantic search heard muffled cries.

Police were under enormous pressure to find the culprit, and their attention was drawn to Blackburn for two reasons. Firstly, as he freely admits, he was a "screwed-up young kid" from a violent, neglectful background, who was attending a reform school in nearby Newton-le-Willows after convictions for burglary and arson. Also, on the weekend in question Blackburn was on home leave, staying only a few hundred metres from where the attack took place.

But aside from a few circumstantial details – for example two haircuts in quick succession which, prosecutors argued, were intended to disguise a resemblance to newspaper descriptions of the assailant – the entire case against Blackburn rested on a confession he hand-wrote on 21 July, after more than four hours of interrogation by two Cheshire detectives.

"It was real good cop, bad cop stuff. All very obvious, but when you're a kid it's terrifying," Blackburn says. This was the fourth time he had been questioned over the case. The only other person in the room was a warden from the reform school. No lawyer was present, and Blackburn was never told he was entitled to one.

After finally breaking down under and "saying things I knew that they'd want to hear", Blackburn wrote a statement which was, he says, effectively dictated to him by the detectives. "They even helped me spell the words I didn't know. My writing was quite basic at the time."

It later emerged that earlier in the investigation, Blackburn's older brother and two other initial suspects had provided police with confessions, all of which were, like his, swiftly retracted.

At his trial the officers insisted the confession was freely offered and in Blackburn's own words. The police "did not tell the truth", the three appeal judges concluded starkly in 2005, noting expert testimony which questioned how a poorly educated 15-year-old could have drafted a document littered with technical terms, all of them spelled correctly.

Glyn Maddocks, the solicitor who guided Blackburn's appeal, says he had never previously seen a more "absolutely black and white case", and is aghast no retrospective action was taken against the Cheshire detectives.

"They lied in court, and they should therefore have been prosecuted. If they did it in that case, did they do it in other cases?" he says.

Blackburn could have been released from jail more than a decade earlier, Maddocks adds, when DNA testing came into use. However, almost all the physical evidence from the police investigation had been lost and there was insufficient DNA remaining for a proper comparison.

If there is one remotely hopeful message to be taken from the case, it is simply the fact that Blackburn is, however chaotically at times, still here, despite years of "prison officers telling me I was going to die in jail, and me believing them".

His demise, he recalls, could have come either at his own hand or through the actions of a fellow prisoner. "The day I walked into prison I become something different. You're not even a normal prisoner. I'm in prison for the attempted murder and sexual assault of a young child. I'm a nonce. You're a beast and an animal, and you're treated as such."

Abandoned by his family, Blackburn says he was "completely and utterly lost within the prison system for nigh on 15 years", with a great deal of this time spent causing as much disruption as possible.

His eventual survival came from a combination of two factors: first, a creeping realisation that "no matter what happened, no matter what they said and no matter what they did, they'd already lost … Because I didn't do it."

He additionally credits the assistance of older, more educated prisoners, who both believed in his innocence and led him towards books.

"I suppose in the end, words were my salvation, because I found I could actually speak, I could actually write, I could actually put my thoughts down on paper. And I did: I wrote and wrote and wrote and wrote and wrote.

"Just fighting the prison system tooth and nail, nose to nose, is fine, it's great, but they can deal with that all day long. What they can't deal with is people fucking thinking. People who can organise. That scares the fucking life out of them.

"And that's essentially what I ended up doing. I started thinking and learning for myself, finding out that I wasn't this fucked-up little scumbag that they thought I was. I was actually quite a nice guy. And I wasn't that stupid either. I found out I could think for myself, I could do things for myself. Essentially, I did start doing that. I started fighting them on their own level."

Despite having lived in the same part of Cornwall for much of his post-prison life, Blackburn has only just acquired his first possession too big to be stuffed into one of the three rucksacks he keeps ready for a quick move. This new exception, a television set, feels like "a millstone around my neck", he complains.

There is also Bonnie, a young collie pup chewing contentedly on a toy at his feet. "I've never been responsible for anything in my life," Blackburn says, almost proudly.