The lawyers in the O.J. Simpson murder case clashed Tuesday over how mixedblood evidence should be presented to the jury.
DNA tests that were performed on blood from the console of Simpson’s Bronco show a mixture of blood belonging to Simpson, his ex-wife Nicole Brown Simpson and her friend Ronald Goldman, prosecutors said.
Prosecutor Rockne Harmon said a glove found at Simpson’s estate after the June 12 murders contained blood from Nicole Simpson, Goldman and, near a cut in the glove, blood from Simpson.
Prosecutor George Clarke also said that blood recovered from the steering wheel of the Bronco was a mixture of blood from Simpson and someone else who may not be connected to the case.
Prosecutor Lisa Kahn said there should be no surprise that genetic evidence from another person showed up on the steering wheel of a car that’s used by other people in the family.
“I assure you there’s no mystery evidence here,” Kahn told Newsday.
Outside the presence of the jury, Simpson’s lawyers argued that prosecutors should not be allowed to present the mixed-blood evidence without proving the statistical accuracy of the tests.
But the prosecution wants to present only the results of the DNA tests and let the jury decide what weight to give to the evidence.
The argument arose during breaks in the testimony of DNA expert Robin Cotton, laboratory director at Cellmark Diagnostics, where most of the testing was done.
Cotton spent the day outlining the differences between the two types of DNA tests and gave detailed explanations of the controls used at Cellmark to prevent and detect contamination, an apparent effort by Clarke to defuse defense attacks on the reliability of the test results.
Cotton noted that crime scene evidence generally is contaminated in some way because it is not collected under sterile conditions, like blood drawn from a donor. She said that once the evidence is at the laboratory it is handled under sterile conditions. But she said that contaminated DNA cannot become someone else’s DNA.
Cotton acknowledged that she could not vouch for the quality of evidence that is sent to Cellmark and conceded that there was no way to determine the age of blood.
Early in the case, Simpson’s defense lawyers said that if Simpson’s blood was found outside his exwife’s condominium it could have been left at a previous date.