In an effort to reverse two days of devastating testimony against O.J. Simpson, a lawyer for the former football great labored Friday to discredit the significance of DNA results that matched Simpson’s genetic markers to blood found near the bodies of his ex-wife and Ronald Goldman.
Earlier this week, DNA expert Robin Cotton testified that a genetic fingerprinting test on a blood drop outside Nicole Brown Simpson’s condominium matched O.J. Simpson’s blood, and that the chance that it was someone else’s blood was one in 170 million.
Cotton, laboratory director of Cellmark Diagnostics, a Maryland company that tested key evidence in the case, also testified that Nicole Simpson’s blood was found on a sock taken from the bedroom of O.J. Simpson’s Brentwood home and that the chance it came from someone else was one in 6.8 billion.
On cross-examination, defense lawyer Peter Neufeld questioned the integrity of the evidence, repeating themes of conspiracy and evidence-tampering that have formed the basis of the defense case.
Neufeld posed several hypothetical situations suggesting that mixups could have occurred at the police crime laboratory and that DNA from swatches of Simpson’s blood collected at his home could have been confused or mixed with swatches of blood recovered from the trail of blood near the bodies.
He also tried to get Cotton to criticize Los Angeles police procedures by comparing methods used at her lab with methods used by police. Citing the process used in the PCR test a narrow DNA test that can be performed on a speck of blood - Neufeld asked about the dangers of contamination by transferring DNA that had been grown in the laboratory to case evidence.
“The PCR amplification test that you utilized doesn’t have the capacity to discriminate whether it’s amplifying the original target DNA or an original cross-contaminant; isn’t that correct?” he asked.
“That’s correct,” Cotton said.
“And since it doesn’t have that capacity, Dr. Cotton, would you agree that even a minute contaminant could be amplified perhaps a million times or more during the amplification process?” Neufeld asked.
The question drew one of many objections from prosecutor George Clarke that was sustained by Superior Court Judge Lance Ito.
But Neufeld pressed on. “Well, as a scientist, Dr. Cotton, have you ever heard the expression, ‘garbage in, garbage out?’ “
Ito sustained another objection, adding, “And I think as lay people, we’ve all heard the expression, too.”
Cotton, who appeared annoyed at times, refused to comment on police evidence collection methods. When Neufeld asked what she thought about storing blood evidence in an unrefrigerated crime scene truck in the middle of June, she said, “We don’t collect it, we don’t have a truck, we just receive it from someone who has collected it.”
The cross-examination is scheduled to continue Monday.