Commonwealth prosecutors say they have no record of ever having known of concerns about the reliability of a top FBI examiner who helped bolster the forensic case against David Eastman.
FBI unit chief Roger Martz gave evidence in the 1995 trial of Mr Eastman for the murder of Assistant Federal Police Commissioner Colin Stanley Winchester in 1989.
Mr Martz, who worked on some of the United States' most important terrorism cases in the 1990s, helped verify the work of a Victorian forensic expert, Robert Barnes, who used now-discredited gunshot residue analysis to link Mr Eastman to the murder scene.
But it recently emerged that the US government, acting on a tip from an FBI whistleblower, began investigating Mr Martz and a group of his colleagues at the FBI Laboratory for misconduct and flawed work less than a year after Mr Eastman's trial.
The final report, delivered in 1997, found Mr Martz was lacking in credibility, objectivity, and competence, recommending that he be found a spot outside the laboratory.
His work on the Eastman case was later reviewed specifically, and was found to be done in a scientifically acceptable manner.
Mr Eastman's legal team never knew of concerns about Mr Martz's credibility. They are now trying to find out who knew of the 1997 report, and when.
Documents suggest the US government alerted its embassy in Australia about the concerns with Mr Martz in 2000 and 2005, asking them to contact relevant Australian officials. US authorities had contact details for a federal police agent and the Commonwealth Director of Public Prosecution's office.
But the Commonwealth DPP told Fairfax Media that it has no record whatsoever of having known about Mr Martz or the US government's concerns.
"The CDPP has reviewed its files and has been unable to identify in its records any documents relating to the veracity and/or reliability of the United States Federal Bureau of Investigation forensic scientist Roger Martz," a spokesperson said.
The CDPP, who did not run the trial against Mr Eastman, said it informed the ACT Supreme Court of this in November.
Both ACT Policing and the ACT Director of Public Prosecutions declined to comment on the issue, saying it would be inappropriate in the face of current court proceedings.