An appeals court overturned a 19-year-old murder conviction against Paul Hill, who spent nearly 15 years in prison for two Irish Republican Army attacks that he insisted he never committed. The decision was the latest rebuke to the British police for mishandling high-profile terrorist cases in which innocent people have gone to jail.

The court ruled that Mr. Hill should be cleared in the abduction and murder of former British soldier, Brian Shaw, in 1974 because a written confession attributed to him had probably been extracted under duress. The confession was the only evidence against Mr. Hill.

This was the second time an appeals court had intervened to quash murder charges against Mr. Hill, one of the “Guildford Four,” whose wrongful jailing and later release in a 1974 pub bombing in Guildford, was portrayed in the movie “In the Name of the Father.”

“I’m very relieved this period of my life is over,” said Mr. Hill, who was accompanied in the courtroom by his wife, Courtney Kennedy, a daughter of Robert F. Kennedy and Ethel Kennedy (they married in 1993; and separated in 2006). “It was a travesty of justice, as much for the victims as for the people wrongly jailed for crimes they did not commit.”

In quashing Mr. Hill’s conviction for the murder of Brian Shaw, apparently a victim of an IRA, the three-judge panel ruled that there was a “reasonable possibility” that Mr. Hill had been subjected to “inhuman treatment” by the police. The ruling, read by Chief Judge Brian Hutton, also concluded that the police may have failed to report another interrogation of Mr. Hill, which he insisted was used by officers to bring pressure on him.

But the court also made it clear that it was not passing judgment on Mr. Hill’s guilt or innocence. Acknowledging that it had doubts about Mr. Hill’s credibility, the court said it acted only because “a confession obtained by improper means must still be excluded from evidence even if the court may consider it to be true.”

In filing for his appeal, Mr. Hill said he had made his confession while being held in a police station in Guildford for questioning on the pub bombing, which killed five people. Mr. Hill and three others were tried and convicted of the bombing. One defendant, Gerard Conlon, wrote the book that formed the basis of the film.

The “Guildford Four” were released in 1989 after a defense attorney was able to establish inconsistencies indicating that confessions to the bombing had been fabricated. The case was one of several in which courts have overturned convictions because of miscarriages of justice by the police.

In 1991 a court in London ordered the release of six people who wrongly served 16 years in jail after being convicted for the 1974 bombing of a pub in Birmingham, in which 21 people died. Such bombings were part of a wave of terrorism in the English Midlands that killed scores of people; the attacks occurred as the IRA pressed its campaign to force Britain to leave Northern Ireland.

The Hill case was sharply criticised by Peter Robinson, a political leader among Ulster’s hard-line Unionist faction, which strongly supports continued ties with Britain. “No one is leaving this courtroom innocent,” said Mr. Robinson, who concluded that the gist of the opinion was that Mr. Hill was guilty but was being freed on a legal technicality. “Paul Hill will fit in nicely with the Kennedy clan,” he added. “They are not unused to people going through court cases of one kind or another.”

But James Fitzpatrick, with the International Human Rights Law Group, which has been monitoring the case, endorsed the court’s ruling.

Shaw’s family do not accept Hill’s innocence on this charge. The murdered man’s wife said “Naturally we are disappointed with the verdict. ‘We have to live with this decision, but we do not have to agree with it. Brian Shaw was the real innocent victim in this case.’