Evidence
Suspected Serial Killer Charged in Only 2 Murders Due to Damaged DNA
Posted May 22, 2009, 12:31 pm CST
By Debra Cassens Weiss
A 72-year-old insurance adjuster said to be a suspect in as many as 30 murders has been charged with just two killings because DNA evidence from the other cases has been damaged.
When John Floyd Thomas Jr. was charged last month, Detective Richard Bengston of the Los Angeles Police Department said he could be “Los Angeles' most prolific serial killer." But now he tells the New York Times he will be investigating for a long time. “This is a career case,” he said.
More traditional investigative techniques will have to be used because DNA found at three other crime scenes yielded less than definitive results, the Times says. The material had deteriorated, yielding only partial matches to Thomas’ genetic profile. Prosecutors are hesitant to file charges, and detectives will have to find corroborative evidence before there will be any additional murder charges, the Times says.
A complete DNA match is usually based on an analysis of 13 locations, or loci, on the human chromosome, the story explains. The odds of two unrelated people sharing the same 13 loci are estimated to be one in four quadrillion.
When a DNA sample is deteriorated, fewer loci can be analyzed, and when there is a match, it is said to be partial. Only three or four loci have been matched in Thomas’ case, Bengston told the newspaper.
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