"A top FBI forensic expert who helped cement the case against David Eastman was embroiled in an explosive misconduct probe that was scathing of his competence and reliability.  Fairfax Media can also reveal that federal police and Commonwealth prosecutors may have known of serious concerns about the FBI examiner's credibility since 2000, but did not pass it on to Eastman, who spent 19 years behind bars on a now-quashed murder conviction. The FBI's chemistry toxicology unit chief Roger Martz​ worked on some of the US' biggest cases in the 1990s; the 1993 World Trade Centre bombing, the OJ Simpson murder trial, the Oklahoma city bombing, and the VANPAC mail bomb assassination of a US judge. ACT prosecutors called Mr Martz as a witness at Eastman's 1995 trial, where he helped bolster the now completely discredited work of Robert Barnes, a Victorian forensic expert who used flawed gunshot residue analysis to link the accused to the scene of Assistant Australian Federal Police Commissioner Colin Winchester's murder.  But less than a year after the trial, Mr Martz and a group of colleagues became the target of an investigation of flawed FBI Laboratory practices, conducted by the US Department of Justice's Office of the Inspector-General. Its final 1997 report found Mr Martz's work was "deficient", that he "lacked credibility and judgment", gave "misleading" evidence, tended to overstate findings, departed from bureau protocols, and failed to use proper thresholds for scientific proof. It found Mr Martz was not fit to be a unit chief, and recommended the bureau either closely monitor him, or find him a job outside the FBI Laboratory. There is so far nothing directly suggesting his work on the Eastman case was flawed. A fellow FBI examiner appears to have reviewed Mr Martz's analysis of physical evidence relating to the case in 2007, and found it was done in a "scientifically acceptable manner". But the revelations raise serious questions about why Eastman's legal team were never made aware of the US government's damning assessment of Mr Martz. The lack of disclosure denied the defence a major opportunity to probe Mr Martz's Eastman work themselves, or raise it in any of the successive appeals or inquiries that have been held since the conviction. It is also unclear why, despite an exhaustive range of subpoenas, nothing about Mr Martz's problems was produced to the 2014 Martin Inquiry into Eastman's conviction. The DPP has placed Mr Martz on the witness list for the potential retrial of Eastman, but it is unclear whether he will be called.  Eastman's defence are now privately demanding to know what the ACT Director of Public Prosecutions, Commonwealth DPP, and AFP were told about Mr Martz, and when.  Documents obtained by Fairfax Media show US authorities were trying to alert the Australian government about Mr Martz through the US Embassy's legal attache as early as 2000, making a second attempt in 2005. .........More recently, the US Department of Justice wrote to the Australian Attorney-General's Department, warning again about their concerns with Mr Martz. The US government, in September last year, asked that the information be passed on to prosecuting authorities so they could decide whether Mr Martz's evidence was relevant, and whether "the defense was apprised of the 1997 [Office of the Inspector-General] report". The text of the report was damning of Mr Martz. It read: "Based on our investigation, we conclude that Roger Martz lacks the credibility and judgment that are essential for a unit chief, particularly one who should be substantively evaluating a range of forensic disciplines," "We found Martz lacking in credibility because, in matters we have discussed above, he failed to perform adequate analyses to support his conclusions and he did not accurately or persuasively describe his work." "We recommend that Martz not hold a supervisory position. The Laboratory should evaluate whether he should continue to serve as an examiner or whether he would better serve the FBI in a position outside the Laboratory. " The problems with Mr Martz may be explored in the current stay application before the ACT Supreme Court. That stay application has been launched by Eastman to try to prevent a second trial for Mr Winchester's murder."