Plaintiffs Grill Defense's DNA Expert
SANTA MONICA, Calif. (Dec. 12, Evening) -- Defense DNA expert John Gerdes Thursday afternoon in the O.J. Simpson civil trial admitted on cross-examination that most of the DNA tests in the case appeared to be reliable. Gerdes conceded that there was "no direct evidence" of contamination in the majority of the tests, but maintained that the Los Angeles Police Department's poor collection procedures made it more likely that the tests could be wrong.
Court will be dark on Friday as the defense and plaintiffs lawyers decide which portions of forensic scientist Henry Lee's videotaped deposition will be shown to the jury. Lee's testimony will be played some time next week. Also scheduled next week: forensic pathologist Michael Baden and Herbert MacDonell, a bloodstain analyst.
On direct examination Gerdes said that DNA tests performed on blood found in Simpson's Bronco, on the Rockingham glove, and at the Bundy crime scene were likely contaminated. He also pointed out a number of improper collection techniques used by criminalist Andrea Mazzola that could have caused cross-contamination of blood samples. But on cross-examination, plaintiffs' lawyer Thomas Lambert asked Gerdes to discuss specific tests, not general procedures. Gerdes admitted that improper evidence collection techniques do not necessarily produce incorrect test results.
Gerdes was also forced to explain why none of the "control swatches" used in the much of the DNA testing showed contamination. When criminalists collect blood evidence at a crime scene they often use two cotton swabs. One swab is used to pick up the blood stain and the other swab is swiped on the area next to the stain. The second swab, called the control, does not have any DNA on it but is tested along side the one that does. If the contamination occurs, the control should have DNA on it.
Noting that none of the control swatches had DNA on them, Lambert asked Gerdes to explain his theory of contamination.
"So, somehow this contamination finds its way onto closed coin envelopes, closed bindles, and only gets on evidence samples and not control swatches?" Lambert asked.
"It would be a systematic sort of contamination," Gerdes replied.
"Shouldn't it get on the control swatches?" Lambert continued.
"[I]t should," Gerdes said.
Lambert also sharply questioned Gerdes about his credentials, noting that Gerdes had never been at a crime scene, never collected evidence, and did not perform DNA tests on forensic evidence. Gerdes, Lambert noted, only testified for defendants "trying to get off on rape or murder charges."
After Lambert's questioning, defense attorney Robert Blasier used most of his redirect to raise concerns about planting of evidence. He contended that the LAPD was "dry-labbing" the control strips -- replacing the actual strips with new ones after the tests were performed. Blasier also brought up the blood samples from the back gate at Bundy and the socks -- both of which were collected later in the investigation.
"Would you agree that the stain on the sock and [from the back gate] are consistent with blood coming from a reference vial?" Blasier asked.
"In terms of the amounts [of DNA], yes," Gerdes replied.
-Robert Schmidt
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