Jurors Receive DNA Lesson
SANTA MONICA, Nov. 13 (Evening) -- The plaintiffs turned to DNA evidence Wednesday afternoon as Robin Cotton, laboratory director of Cellmark Diagnostics, took the stand. Cotton gave an hour overview on DNA testing before beginning to discuss the results from her laboratory's tests of blood evidence from the case.
Thursday morning Cotton will continue to testify on direct examination. Gary Sims, a California forensic scientist, and Renee Montgomery, a criminalist from the California Department of Justice Laboratory, are expected to take the stand after Cotton.
Cotton told the jury that a blood drop near the bodies of Nicole Brown Simpson and Ronald Goldman contained DNA patterns that matched Simpson's in five locations. According to the Cellmark test, known as an RFLP test, the chance the blood belonged to someone other than Simpson is one in 170 million to one in 1.2 billion. A blood drop found in the foyer of Simpson's Rockingham estate also had the same odds of belonging to Simpson, Cotton said.
The RFLP test "gives the most information you can get" from a DNA test, Cotton told the jury.
Cellmark labs also performed less conclusive DNA tests, known as PCR tests, on several other blood drops found at the Bundy crime scene. The likelihood the blood belonged to someone other than Simpson fell in the range of 1 in 5,200 to 1 in 56,000. Cotton also discussed PCR tests conducted on nail scrapings from Nicole Simpson's hands. The blood on the nails most likely belonged to Nicole Simpson, and there was no evidence of an additional person's blood mixed in, Cotton said.
Before presenting the results of Cellmark's DNA tests, plaintiff's lawyer Thomas Lambert took Cotton through a quick, but dense, description of DNA testing. Almost from the outset Cotton's testimony was mired in a thick, alphabet soup as she talked about TWGDAM guidelines, AT pairs, GC pairs, RFLP tests, PCR tests, and DQ Alpha tests.
Lambert also took a preemptive strike at a probable area of defense attack -- the degradation of the evidence. He asked Cotton to explain the term as it relates to DNA tests.
"Degradation is something you see all the time," Cotton said, comparing a DNA molecule to a long piece of string. If the string is cut 20 times, Cotton explained, it would be slightly degraded. However, it is still possible to conduct tests on DNA that has been degraded. Only the most severely degraded DNA cannot be tested, Cotton said.
Robert Schmidt
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