Roger Martz, an FBI Special Agent in the Chemistry Unit, testified over two days in July 1995 about his EDTA testing of blood evidence — work that went to the heart of the defense's claim that blood on the sock and back gate had been planted from preserved reference samples. Defense attorney Robert Blasier methodically attacked Martz's methodology, exposing destroyed data, undocumented procedures, and a flawed quantification approach, including Martz's decision to combine two unknown samples before testing and his use of a less sensitive testing mode. Prosecutor Marcia Clark fought to rehabilitate him by drawing out clear EDTA signals in reference blood versus evidence blood, but Martz's credibility visibly deteriorated under the sustained cross-examination.