The Appeal Court in England has cast doubt on the expertise of a forensic scientist who challenged DNA evidence at the Omagh bomb trial.
Professor Allan Jamieson, who appeared as a defence witness for Sean Hoey, testified that low copy number DNA was unreliable.
The process, which allows genetic profiles of offenders to be created from very small tissue samples uses techniques only available since1999.
Delivering his judgement on Mr Hoey, Mr Justice Weir accepted the argument Prof Jamieson had put forward with another scientist, that the science of low copy number DNA had not been "validated" by the international scientific community. He said it was "unreliable" and test results were open to interpretation.
However appeal court judges in another case have largely agreed that the professor is not qualified to give expert evidence.
Prof Jamieson said he would consider the judgement carefully.