Police have refused to apologise to a man wrongly jailed for 25 years because officers lied at his trial, even after the now-retired appeal court judge who quashed the conviction told the Guardian that the force should say sorry.

Cheshire police said that while they were “concerned” at the wrongful jailing of Paul Blackburn, who was convicted as a teenager in 1978 for the attempted murder and sexual assault of a young boy, no apology was needed as procedures at the time of the investigation were “very different”.

Blackburn, then in a reform school in Warrington, Cheshire, was arrested shortly after he turned 15. The only notable evidence against him was a confession he signed after four hours of questioning by two senior officers, with no parent or lawyer present.

The appeal court, which quashed the conviction in 2005, two years after Blackburn was released on license, said the police claim he wrote the confession unaided “can now be seen to have been untrue” after linguistic analysis showed it was littered with police jargon almost certainly unknown to a poorly-educated teenager. The ruling said this cast doubt on other police claims.

The Guardian covered Blackburn’s case for its Justice on Trial series in 2009. In follow-up interviews recorded for the Today in Focus podcast, the lead appeal court judge, Sir David Keene, recalled it as “a shocking case”.

Keene, who is now retired and thus able to speak publicly for the first time, said the evidence about Blackburn’s confession was “manifestly absurd” and that the police should apologise.

“In the light of the findings of our court about the way in which some of the officers of that force had lied at trial, leading to a wrongful conviction, I would have thought it would have been appropriate for them to apologise,” he said.

When asked about Keene’s view, assistant chief constable Matt Burton said the Cheshire police would not do so, despite accepting the appeal court decisions. Burton said the force was “satisfied that we do not need to reopen the investigation”, an apparent intimation they still believe Blackburn was responsible.

“An independent investigation into the conduct of the officers involved in this case was also undertaken in 1996 which concluded that there was no evidence of any misconduct nor was there any evidence to pursue criminal proceedings against the officers concerned,” Burton said.

“This case was investigated more than 40 years ago, at a time when the procedures and rules around the questioning of suspects and the submission of evidence were very different to that of today.”

Blackburn’s ordeal in more than a dozen prisons over his sentence was made even worse by his refusal to accept the protection offered to sex offenders because he maintained his innocence.

Over his first 15 years in jail, Blackburn said, he endured “beatings on a daily basis, abuse on a daily basis, spit on a daily basis”, adding: “The first time I was placed on report officially by a prison officer, was for refusing a direct order to mop my own blood up off the floor.”

Blackburn was later assisted by older, more educated prisoners, who helped him push for an appeal. While he has worked since his release to highlight other miscarriages of justice, Blackburn has described how he still struggles to cope with the trauma of his experiences in prison.

“I still get quite distressed, on a daily basis, replaying things over and over again,” he said. “You’re standing there doing the ironing, and all of a sudden your in Full Sutton [jail], in the punishment block. Different things will set me off – uniforms, keys, all this sort of thing.”

Some semblance of stability has been brought by marriage, and by compensation Blackburn was awarded after the appeal – though changes to the system made under the 2010 coalition government means it would be unlikely he would be awarded this now.

Paul Blackburn’s story can be heard here on Today in Focus