Seamus Daly is released from Magheraberry Prison on Tuesday in Ballymena, Northern Ireland. The 45-year-old laborer was accused of murdering 29 people in the 1989 Omagh bombing, but the case collapsed in court Tuesday when prosecutors decided there was no reasonable prospect of conviction. (Charles Mcquillan/Getty Images)

The man charged with murdering 29 people in a car bombing in the Northern Ireland town of Omagh walked free from prison Tuesday after prosecutors concluded that the evidence against him — particularly a witness who was supposed to place him in the area that day — was too weak.

Seamus Daly had spent nearly two years in prison awaiting trial for the Aug. 15, 1998, attack on a crowd of shoppers, workers and tourists. His case joined a string of failed prosecutions against figures with a group known as the Real IRA who have long been blamed for the deadliest single bombing of the Northern Ireland conflict.

Daly, 45, did serve a brief prison sentence in Ireland after pleading guilty in 2004 to membership in the Real IRA, one of several outlawed factions, each of which styles itself as the “true” Irish Republican Army. These small, feud-prone gangs reject the cease-fire observed since 1997 by the major group, the Provisional IRA.

The Real IRA planted a string of car bombs in Northern Ireland towns in 1998 in a bid to undermine support for that year’s Good Friday peace accord, which sought to end a three-decade conflict that claimed 3,700 lives. Police prevented deaths in several other car bombings with swift evacuations.

But on that unusually sunny Saturday in Omagh, police responding to vague telephone warnings ordered people away from the town’s hilltop courthouse and down Market Street — straight toward the bomb parked outside a shop selling school uniforms. Most of those slain were women and children, including a mother pregnant with twins.

In this Aug. 16, 1998 photo, police stand amongst the rubble after a car-bomb attack in the Northern Ireland town of Omagh. (Dan Chung/Reuters)

Public horror over the Omagh atrocity spurred an island-wide security crackdown on those IRA factions that refused to back the peace accord. The British and Irish prime ministers and U.S. President Bill Clinton visited the blast scene and vowed to isolate the extremists. But in the nearly 18 years since then, those factions remain active and Omagh has become a byword for justice denied.

Police have testified in court that telecommunications records document how a cellphone allegedly used by Daly traveled across the Irish border to Omagh on the day of the attack. A witness, Denis O’Connor, who previously testified that Daly used that phone to call him from Omagh a half-hour after the blast, performed badly on the stand last week during a preliminary hearing designed to test evidence.

“He sounded not a credible witness at all, a very untruthful witness. I would not want anybody to be convicted on that evidence,” said Michael Gallagher, who has campaigned since 1998 for the Real IRA bomb unit responsible for the incident to be brought to justice. Nobody has been successfully prosecuted for the crime.

Gallagher, whose 21-year-old son Aiden died in the attack, noted that three high-profile attempts to convict alleged members of the Omagh bombing team have failed because of weak, disputed or overturned evidence.

Daly’s lawyer, Peter Corrigan, compared the prosecutors’ case to “a house of straw.” He said O’Connor committed perjury, while police had misrepresented their evidence on mobile phones used by the attackers.

In 2009, a Belfast civil jury found Daly and three other Real IRA figures responsible for the bombing and ordered them to pay about $2.5 million in damages, a judgment that was upheld on appeal in 2013. They have refused to pay.

In 2007, electrician Sean Hoey — who had faced 56 charges, including construction of the Omagh bomb’s power-timer units and 29 counts of murder — was acquitted on all charges after a Northern Ireland judge rejected forensic evidence and said police witnesses had lied. Hoey had spent four years behind bars awaiting trial.

In this 1998 photo, friends and family carry the coffins of Avril Monaghan and her 18-month-old daughter, Maura, to a church in Augher, northern Ireland. The mother and daughter were among 29 people killed in the Aug. 15, 1998 car bombing in the Northern Ireland town of Omagh. (Dylan Martinez/Reuters)

In 2002, pub owner Colm Murphy was convicted of supplying the phones used by the bombers and received a 14-year prison sentence in Ireland. His conviction was overturned on appeal eight years later, after two detectives admitted they had rewritten their interrogation notes to remove conflicts in information.