Prosecutors have given jurors 170 million reasons to convict O.J. Simpson.
Scientist Robin Cotton said Thursday that only one in 170 million black and white people have the genetic blueprint of Simpson's blood and a small drop of blood found near the bodies of Simpson's ex-wife and her friend.Calculated another way, the prosecution's DNA tests showed there are only a few people on Earth with the same genetic makeup of blood found at the murder scene - and one of them is Simpson.
Under cross-examination, Cotton acknowledged that her astronomical figures ignore possible tampering or contamination and do not say when or how the blood was deposited.
Nevertheless, some legal analysts said the evidence was so compelling that, after about three months of testimony, prosecutors have presented all they need to obtain a guilty verdict that would stand up on appeal.
"They have met their burden of proof, legally speaking," said Loyola University law professor Stanley Goldman. "If the prosecution wanted to end it here, they could end it here."
It doesn't end here, of course, not by a long shot.
There is still the cross-examination of Cotton, which continues today after a shaky start Thursday. The low point was the judge slamming down his hands in anger and ordering one attorney from each side to pay $250 in sanctions - on the spot - for making improper comments in front of the jury.
There also is much more DNA testimony still to come from a scientist at the California Department of Justice laboratory, which tested many items collected in the case.
And, finally, the defense has yet to present its case, with the big question being whether Simpson himself will take the witness stand.
During the cross-examination, defense attorney Peter Neufeld offered a hypothetical situation in which blood swatches were contaminated with other blood during police laboratory handling.
"So if the samples were subject to cross-contamination, those numbers wouldn't mean anything?" Neu-feld asked Cotton.
"They mean what they mean," Cotton responded. "They don't mean anything else."
She acknowledged there is no test to determine the age of blood drops and none to detect tampering before samples arrive at her laboratory. The defense has suggested a detective smeared Nicole Simpson's blood on a sock at the foot of Simpson's bed and someone else sprinkled Simpson's blood about the crime scene and his mansion.
Nicole Simpson and Ronald Goldman were knifed to death outside her condominium on June 12.
Cotton, director of the Cellmark Diagnostics lab, has led jurors down an elaborate blood trail toward Simpson. Speaking in the unemotional, analytic tone of a teacher, she used complex calculations to closely link Simpson to five drops of blood collected from the crime scene and his mansion.
Jurors appeared riveted by the testimony, gazing at charts and taking copious notes. Twice they were trotted out of the jury box to look closely at DNA X-rays mounted on a light box.
Cotton's most astronomical figures involved a pair of socks found near Simpson's bed. Cotton said one sock contained the DNA type of Nicole Simpson. Asked how many other whites shared that DNA type, Cotton said one in 9.7 billion.
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Additional Information
DNA test results
Two types of DNA testing showed almost certain matches between O.J. Simpson's blood and blood swatches collected as evidence in the murders of his ex-wife and her friend last June.
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Blood found in O.J. Simpson's foyer.
Odds of a match: 1 in 170 million
O.J. Simpson's blood
Blood on a sock found in O.J. Simpson's bedroom
Nicole Simpson's blood
Odds of a match: 1 in 9.7 billion
Other blood matches
Nicole Brown Simpson
A bloody shoeprint leading from the bodies
Blood under her fingernails
Blood on the bottom of victim Ronald Goldman's shoe
O.J. Simpson
A drop of blood found on a pathway at the crime scene.