The case against Sean Hoey began to unravel right from the beginning.
To secure a conviction more than eight years after Northern Ireland's single worst terrorist atrocity was always going to be difficult, but a series of flaws in the prosecution evidence and police investigation were quickly exposed, making an acquittal near inevitable.
The case against Hoey was based on a series of supposedly complementary pieces of evidence. While the prosecution never had a smoking gun they believed that the totality of their evidence would prove the unemployed electrician was the man who built the Omagh bomb and a series of other Real IRA devices.
However, as the defence began to pick apart the individual strands of the evidence, the prosecution case quickly unravelled. Time and again damning flaws in how evidence was gathered by police and army during the Real IRA bombing campaign in 1998 were exposed in court.
The verdict will have dealt a powerful blow to the investigatory prestige of the PSNI and is a sickening blow to the Omagh families who are still waiting for justice.
On the first day of the marathon trial serious concerns were raised about how forensic evidence was stored and labelled. It scarcely got any better for the prosecution after that.
Low copy number DNA
Much of the case against Sean Hoey rested on the controversial new technology of Low Copy Number DNA testing.
This technique enables scientists to produce DNA profiles from samples expected to contain very few cells, even if they are too small to be visible to the naked eye.
As part of the Omagh investigation, LCN DNA testing had been carried out on a number of the 1998 devices. Hoey consented to provide buccal swabs to be tested.
Scientists believed they found DNA matches between Hoey and samples from the devices at Lisburn, Armagh police station, Blackwatertown and Altmore.
At the beginning of the trial, lead prosecution barrister Gordon Kerr QC stated: "It is submitted that the extent of the DNA findings is such as to exclude the reasonable possibility that the findings could be explained in an innocent way."
However, the DNA argument floundered in a wave of doubts over reliability of tests and fears of contamination.
LCN DNA is a relatively new scientific technique and it requires painstaking levels of forensic precautions to be taken by those who are gathering and storing evidence. In 1998 the teams investigating Omagh and other Real IRA bombings could not have taken precautions for a scientific method which had not yet been invented. Thus the contamination argument became overwhelming.
At one point in the trial, a top forensic expert admitted that Hoey's DNA may have contaminated evidence after tape was removed from his house and compared with tape from the scenes of the explosions.
The defence went further and attacked DNA evidence on the grounds that exhibits were tampered with. Photographs showed that black tape had been allegedly placed on the lid of a timer power unit after it was examined by forensic experts. When no explanation was provided for this, trial judge Mr Justice Weir mused that maybe it was a "Houdini thing".
Moreover, the reliability of LCN DNA as an evidential tool was never accepted by court. Defence argued that besides two forensic labs in the UK and one in Holland and New Zealand, no other labs in the world used the technique. They also pointed out that the FBI used LCN DNA only for intelligence and not for evidential purposes. In the US such tests are not allowed to be included on the country's national DNA database.
Defence barrister Orlando Pownall said that instead of consensus for LCN DNA testing there was confusion, shades of grey, an inexact science and the court could not be expected to speculate on it.
The shortcomings in the police investigation into the Real IRA bombing campaign severely undermined the prosecution case against Hoey. A series of allegations about the poor handling and interfering with evidence were presented to court.
Early in the case a senior detective apologised for ordering the destruction of parts of a mortar bomb which had been fired at Grosvenor Road RUC station in 1998. Another officer told the court he had no idea why dates on a label attached to evidence seized from the scene of a planned car bomb attack on Armagh police station had been changed.
Worse was to come. A senior detective, Philip Marshall, who had investigated an attempted bombing at Altmore Forest admitted that his approach to evidence was "slapdash" and that he had asked a colleague to " beef up" a witness statement. Police were accused of interfering with witness evidence after separate versions of the same statement were produced, the latter emphasising that forensic precautions had been taken by police investigating the attempted bombing. The defence accused police of a conspiracy to "bury" evidence in relation to explosive offences.
In one of the most dramatic moments of the trial, Scenes of Crimes Officer Fiona Cooper handed her passport into court to prove that she was in Zambia on the date on which she was supposed to have made a statement about the Altmore incident.
The prosecution were later to accept that question marks hung over the reliability of some of their main police evidence while the judge described the conduct of two police witnesses as "reprehensible". Mr Justice Weir said DCI Marshall and a SOCO Cooper had provided "false and misleading evidence". They are both now the subject of a Police Ombudsman investigation.
The judge also called for a full investigation into why police statements relating to Altmore had been altered or lost.
Mark 19 timer power units
There were strong similarities in the Omagh bomb and a number of other Real IRA explosive devices planted in 1998. Most of them used Mark 19 Timer Power Units (TPUs). The prosecution believed that they could prove that the devices were so similar in construction that they were bound to have been made by the same person. In court they produced senior forensic scientist Dennis McAuley. After inspecting the way the maker had soldered the wires and connections in 47 explosive devices he told the court "I believe there is support for the proposition that the Northern Ireland 1998 units were made by the same person rather than a group of people sharing knowledge" .
However trial judge Mr Justice Weir dismissed Mr McAuley's conclusions as " guesswork" and refused to allow them to be entered as evidence. The judge said he accepted the scientist's physical findings but added "Mr McAuley, in my opinion, brings nothing by way of expert opinion to the interpretation of these results".
The prosecution believed that fibres recovered from glue in six of the explosive devices proved that they had been made in the same environment. Fibres were also recovered from Hoey's home in Molly Road, Jonesborough. However, the expert witness said this only provided "weak" support that he had been in contact with the devices.
Furthermore, top London defence barrister Orlando Pownall claimed in court there was no fibre evidence to connect Hoey with any of the devices nor did it provide corroboration to any other evidence.
A voice analyst was due to be called by the prosecution to compare the voice on a recorded bomb warning with that of Hoey. During their opening of the case the prosecution claimed that the expert would surmise that the voice was more likely to be his than not. However, doubts surrounded this evidence and it was never introduced in court.