Dr Martinelli explains that DNA recovery from gloves depends heavily on how they were removed – and whether biological material was preserved inside. "You're going to get the DNA from inside of the glove, not outside of the glove," he says. "It really depends on how the person removes the gloves."
If latex gloves are pulled off in a way that turns them inside out, the interior – where sweat and skin oils are present – may be better preserved. "When you sweat, you sweat water and you also sweat oil," he explains. "So we can definitely get DNA from that."
He notes that even if initial testing did not produce a match, advances in forensic science mean evidence can continue yielding results long after it is first collected.
You're starting to see now cases that are 30 years old that could not be solved before are now being solved because they're running the cold case DNAs through the new DNA technology," he says.
Beyond standard DNA comparisons, Dr Martinelli points to the growing role of genealogy databases in modern investigations.
"With genealogy, you may not get the person, but you're going to get a relative of the person," he says. "And then that really narrows down your search." He adds that the key step will be ensuring any viable DNA is submitted to the FBI’s CODIS database.
After investigators confirmed gloves recovered near the scene did not contain matching DNA from inside Nancy Guthrie's home, forensic consultant Dr. Ron Martinelli explains why the case is far from over
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