An urgent review into thousands of criminal cases was launched by the Crown Prosecution Service yesterday after the credibility of an advanced form of DNA testing was called into question by the judge in the collapsed Omagh bomb trial.
All current cases in which Low Copy Number (LCN) DNA testing forms part of the evidence will be immediately scrutinised after the acquittal on all charges of Sean Hoey, the only man brought to trial for the 1998 attack in which 29 people died.
The development could open the floodgates to thousands of appeals and could also mean certain prosecutions may not be brought to court, unless other evidence is found to be compelling.
Last night, the Association of Chief Police Officers (Acpo) announced that it was suspending the use of LCN testing in all future cases pending the outcome of the CPS review.
But there will be pressure on the Justice Department to order a review of all cases where LCN DNA testing has been used to see if there have been miscarriages of justice.
The technique, which enables the analysis of a small number of cells, had been hailed as a major breakthrough that would allow DNA to be obtained from samples which hitherto had proved impossible.
But Mr Justice Weir refused to accept the technique as reliable evidence in the Belfast High Court on Thursday when he freed Mr Hoey, from South Armagh, due to a lack of evidence, saying he had decided the method was not yet at a sufficiently scientific level to be credible.
The reverberations of the verdict are being felt far beyond Belfast. As well as the CPS, the Forensic Science Regulator ordered a review, saying it had started using LCN DNA routinely in 1999 and had now used it 21,000 times. Not all of these were UK cases and it has not been the only evidence, it added. But the number of verdicts that could be appealed against may be high.
Acpo had expressed concern to the Home Office over the technique in a confidential report in August after it had instructed two experts to examine LCN DNA testing. An internal Acpo memo called on the Home Office forensic science regulator to "facilitate the creation and adoption of a national minimum technical standard for low-level DNA process such as LCN". It was marked in bold type: "This should be carried out as a matter of urgency."
Professor Brian Caddy, who compiled an independent review for the Home Office of the forensic failures in the Damilola Taylor case, is conducting the review of LCN DNA testing and his report is expected in February. He will be taking evidence from international experts who have been sceptical about the technique.
In the Damilola Taylor case, Professor Caddy found no systemic errors at the FSS, but concluded that human error by scientists was responsible for missing a crucial blood-spot on a trainer that eventually led to a fresh prosecution and conviction.
Last year, a joint statement by the Home Office and Acpo said: "Towards the end of 2006, we became aware that a small percentage of DNA samples may need to be re-examined as a result of differences in the way forensic suppliers were using new techniques to analyse forensic material between 2000 and 2005."
Sir Hugh Orde, the Chief Constable of Northern Ireland, has ordered a review of all cases in the province involving LCN DNA evidence. He said: "I have asked for an urgent review of all cases that rely in any way, shape or form on LCN DNA." He said it was at the cutting edge of science and had been used in the Omagh charges because of his determination to do everything he could to build a case.
Shaun Woodward, the Secretary of State for Northern Ireland, said LCN DNA testing was used singly and independently as evidence in cases only rarely. That will not prevent offenders, some still in prison, from lodging appeals.