Lee explains in "Blood Evidence" why he rejected Scheck’s contamination claim. Scheck claimed that contamination could happen from repeated use of the reagents for Amplification but all the reagents tested negative for contamination. Petrocelli wrote in "Triumph of Justice" that Scheck’s witness John Gerdes lied when he said that Collin Yamauchi spilled Simpson's blood in the lab. Scheck then suggested that the victims blood in the Bronco could be the result of contamination in the LAPD crime lab but Lee wrote in "Blood Evidence" the second collection from the Bronco returned the same matches as the first collection, proving they weren't contaminates. M. L. Rantala wrote in "OJ Unmasked" that Scheck implied that the evidence locker was in the PCR amplification room when he had Gerdes testify that Yamauchi took the PCR extraction product back to "the same location" so his contamination claim would be plausible. Lee wrote in "Blood Evidence" that "Gerdes conceded the PCR extraction product was not returned to the specific area near the extraction room or evidence-handling area but was taken to a completely separate area located a comfortable distance away making a contamination scenario highly improbable". Scheck also contradicted himself when he claimed it was impossible to distinguish blood from the reference vials from blood from the body despite demonstrating just that the week prior using EDTA. Scheck argued that all of the contamination occurred through random carelessness in the lab and but the only three valid matches were the same three the defense claimed were planted while the remaining 58 matches were all false positives despite that never having happened before. The substrate controls that are used to determine if contamination like he was suggesting occurred were also coincidentally all false negatives so Scheck was claiming that the contamination only got on the evidence items despite they and the substrate controls all being handled interchangeably at the same time. Clinical molecular geneticist Dr. Brad Popovich called Schecks claims "ridiculous". Lee published "A Systematic Analysis of PCR Contamination" which concluded that "no significant contamination occurs from random carelessness".