The decision not to reveal the criminal record of the man accused of murdering Arlene Arkinson has been backed by a retired High Court judge.
Robert Howard is serving a life term for murder
The Public Prosecution Service carried out an inquiry into the 2005 trial of Robert Howard, 62, who was cleared of murdering Arlene, 15.
Howard is serving life for the rape and murder of a 14-year-old London girl.
Sir John MacDermott said the decision not to make the jury aware of his previous convictions was correct.
In a report into the trial he said the prosecution could not link the schoolgirl's death to other crimes by Howard because Arlene Arkinson's body has not been found, so it was not possible to establish exactly how she died.
But he said Robert Howard could face a retrial if her body is found and there is evidence to link the killing to other crimes he has committed.
Arlene, 15, vanished near her home in Castlederg after attending a disco at Bundoran in County Donegal with friends in August 1994. Howard formerly lived in Main Street in Castlederg.
At his trial for her murder, details of his criminal record were not revealed.
He was acquitted by a majority verdict of 10 to two.
Three months later, a reporting restriction was lifted revealing a 40-year history of past convictions for rape, murder and child abuse.
The Public Prosecution Service could have asked a judge to consider making the trial jury aware of Howard's previous convictions, but decided not to do so.
In October 2003, Howard was found guilty of murdering Hannah Williams, from Deptford, in south London, whose body was found in a cement works in Northfleet, Kent, in March 2002.
At the time, it was confirmed that police in both Ireland and England suspected he might be linked to the disappearance of up to six women.
Police investigating the disappearances sought permission to interview him.
It is understood that Irish police have reopened two missing person cases.
After Arlene Arkinson's disappearance, extensive searches were carried out. However, no firm evidence of the teenager still being alive was ever found and her body has not been discovered.