Forensic experts think that key evidence was compromised
Just a day after the LawNewz report dropped, four forensic experts condemned the scientific methods used in the Avery case in an article for the Pittsburgh Post-Gazette. They believed the prosecution unfairly influenced DNA analyst Sherry Culhane and FBI chemist Marc LeBeau to deliver results supporting a guilty verdict, thereby compromising their analysis. They also took issue with LeBeau's wording in his testimony.
As you may recall, LeBeau was brought in to settle one of the more contentious aspects of the case: whether Avery's blood recovered from the crime scene was fresh or planted from a vial. If it came from the vial police collected during Avery's trial for rape in 1985, it would contain traces of EDTA, a chemical preservative. LeBeau could not detect EDTA in three of the six samples and thus concluded "within a reasonable degree of scientific certainty" that it was entirely absent… even though he never tested the remaining three blood stains.
"There is a saying among scientists that absence of evidence isn't necessarily evidence of absence, and that appears to be the case here," the scientists wrote. "It was problematic for Mr. LeBeau to draw conclusions with any scientific certainty about all six of the stains after testing only three of them."