to seven hours after collection. This, they argued, would allow bacteria to degrade all of the "real killer(s)" DNA and thus make the samples more susceptible to cross-contamination in the LAPD crime lab. The prosecution denied that the mistakes made by Fung and Mazzola changed the validity of the results. They noted that all of the evidence samples were testable and that most of the DNA testing was done at the two consulting labs, not the LAPD crime lab where contamination supposedly happened. Since all of the samples the consulting labs received were testable, while Scheck and Neufeld's theory predicted that they should have been inconclusive after being "100% degraded", the claim that all the DNA was lost to bacterial degradation was not credible. The prosecution denied that contamination happened in the LAPD crime lab as well because the result would be a mixture of the "real killer(s)" DNA and Simpson's DNA but the results showed that only Simpson's DNA was present. The prosecution also noted the defense declined to challenge any of those results by testing the evidence themselves. Marcia Clark called Scheck and Neufeld's claims a "smoke-screen". The contamination claim was made by microbiologist Dr. John Gerdes. He testified on August 2, 1995, that Forensic PCR DNA matching is not reliable and "The LAPD crime lab has a substantial contamination problem. It is chronic in the sense that it doesn't go away". Gerdes testified that because of the LAPD's history of contamination, he would not consider any of the PCR DNA matches in this case reliable because the tests were carried out by the LAPD. He also claimed that the consulting labs’ PCR DNA matches were not reliable, as the evidence they tested went "through the LAPD" for packaging and shipping. Gerdes believed only three of the DNA matches to have been valid, which were the same three the defense alleged were planted by the police. During cross-examination, Dr. Gerdes admitted there was no evidence that cross-contamination had occurred and that he was only testifying to "what might occur and not what actually did occur". He accepted that the victims' blood was in the Bronco and Simpson's blood was at the crime scene and neither was due to contamination. He also conceded that nothing happened during "packaging and shipping" that would affect the validity of the results at the two consulting labs. The prosecution implied that Gerdes was