not a credible witness: he had no forensic experience and had only testified for criminal defendants in the past and always said the DNA evidence against them was not reliable due to contamination. Clark also implied that it was not a coincidence that the three evidence items he initially said were valid were the same three the defense claimed were planted while the other 58 were all false positives and the 47 substrate controls, which are used to determine if contamination occurred, were all false negatives. Defense forensic DNA expert Dr. Henry Lee testified on August 24, 1995, and admitted that Gerdes's claim was "highly improbable". Barry Scheck's eight-day cross-examination of Dennis Fung was lauded in the media. However, Howard Coleman, president of Seattle-based forensic DNA laboratory GeneLex, criticized Scheck's cross-examination as "smoke and mirrors" and stated "Everything we get in the lab is contaminated to some degree. What contamination and degradation will lead you to is an inconclusive result. It doesn't lead you to a false positive". Police conspiracy allegation The defense initially only claimed that three exhibits were planted by the police but eventually argued that virtually all of the blood evidence against Simpson was planted in a police conspiracy. They accused prison nurse Thano Peratis, criminalists Dennis Fung, Andrea Mazzola, and Colin Yamauchi, and Vannatter and Fuhrman, of participating in a plot to frame Simpson. In closing arguments, Cochran called Fuhrman and Vannatter "twins of deception" and told the jury to remember Vannatter as "the man who carried the blood" and Fuhrman as "the man who found the glove". EDTA The only physical evidence offered by the defense that the police tried to frame Simpson was the allegation that two of the 108 DNA evidence samples tested in the case contained the preservative Ethylenediaminetetraacetic acid, or EDTA. Ironically, it was the prosecution who asked to have the samples tested for the preservative, not the defense. The defense alleged that the drop of blood on the back gate at the Bundy crime scene, which matched Simpson, and the blood found on a pair of socks in Simpson's bedroom, which matched Brown, were planted by the police. In order to support the claim, the defense pointed to the presence of EDTA, a preservative found in the purple-topped collection tubes used for police reference vials, in the samples. On July 24, 1995, Dr. Fredric Rieders, a forensic toxicologist who had