A former US Secret Service forensics expert testified Tuesday that documents being used by the prosecution against accused Nazi guard John Demjanjuk appear genuine.Larry Stewart, who analyzed 22 documents being used in the case in 2000 by the US Department of Justice’s Office of Special Investigations, told the Munich state court that he found no evidence they had manipulated. Stewart testified over the objections of Demjanjuk’s defense team, who had argued that he should not be used as an expert witness because of his association with the OSI, which investigated Demjanjuk in the United States.