DNA Is a Low-Profile, but Critical, Component of Case

While the media have concentrated on whether Detective Mark Fuhrman is a racist or Kato Kaelin is a flake, what may be the most important evidence in the O.J. Simpson trial has been pretty much ignored.

This is the scientific search for clues in the trail of blood that prosecutors say led from Nicole Brown Simpson’s patio to O.J. Simpson’s Bronco, through his front door and into his bedroom.

While the spotlight of publicity focuses on F. Lee Bailey’s bellowing, the family problems of Marcia Clark and Johnnie Cochran and Chris Darden’s smoldering tempers, most of us have forgotten the two high-powered attorneys the D.A.’s office has imported to run the science side of the case--Alameda County’s Rock Harmon and Woody Clarke from San Diego County.

Nor is anyone closely tracking the activities of the defense team, led by UC Irvine professor William C. Thompson, famed forensic attorneys Barry Scheck and Peter J. Neufeld and Sacramento lawyer Robert D. Blasier, who, before practicing DNA law, was director of enforcement for the California Fair Political Practices Commission.

These attorneys have been locked in an incredibly complicated battle in closed-door hearings before Judge Lance A. Ito, and occasionally in court, over DNA during the last few weeks.

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The rapidly changing and uncertain nature of such evidence was recently illustrated when the California Supreme Court decided it would hear a case over whether the cops can nail a suspect with DNA--deoxyribonucleic acid, the molecules that shape us as separate and distinct individuals.

The high court agreed to take up the case of Sergio Venegas, who was convicted of raping a woman at a Bakersfield Red Lion Inn in 1989. It may take too long for the Supreme Court to decide Venegas’ fate to influence the Simpson trial, but a ruling could come soon enough to affect an appeal or, in the event of a hung jury, a second trial.

Semen taken from the victim’s vagina and the bed pointed to Venegas as the rapist, an FBI criminalist said. That was the main evidence. The victim could not identify the rapist.

The criminalist matched the DNA in blood taken from Venegas with DNA in the semen. In this laboratory process, the DNA is placed on a sheet of film. The developed film shows the DNA looking something like the supermarket price bar code on a can of soup. Venegas’ supermarket bar code matched that from the semen.

This did not prove to a certainty that Venegas, a Latino, was the rapist. According to the FBI expert, statistical studies showed that only 1 person out of 30,000 would have the same DNA pattern as Venegas. But the defense, using a different statistical method, calculated that the odds could be as low as 1 in 35. Thus, Venegas’ lawyers said, someone else could have committed the crime.

Santa Monica attorney Paul Mones, another DNA expert, said the gap separating the estimates was so great because the prosecution and the defense used different statistical formulas. One formula produced odds favorable to the defendant while the other was against him.

The vast difference in statistics shows that DNA evidence may not be as clear-cut as proponents have maintained. This statistical gap may have persuaded the Supreme Court to consider the issue, for California judges have been slower than colleagues in other states to accept DNA.

“California has always taken a conservative approach,” said Southwestern University law professor Myrna S. Raeder. “We are not willing to use these kinds of evidence unless we are convinced they are accepted by the scientific community.”

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Just how the statistical dispute will play out in the Simpson trial was explained to me by Seattle DNA expert Howard Coleman, co-author of the book “DNA in the Courtroom: A Trial Watcher’s Guide.”

Figure, he said, that the prosecution will flash pictures on the big screen to show that the DNA patterns in Simpson’s blood match patterns in blood found at the death scene. Other big screen slides will show that the DNA patterns in the victims’ blood match those in blood found in the Bronco and at Simpson’s estate. Prosecutors will come up with high odds--statistical studies showing that one person in 1 million has these DNA profiles.

The defense will low-ball it with the Simpson numbers, coming up with something like 1 in 100,000 or even 1 in 20,000.

This will come on top of other defense attacks on the DNA evidence--that the prosecution laboratories made analytical errors, that the samples were contaminated or that the cops even tampered with the evidence.

For a layman like me, who barely scraped through science in school in the pre-DNA era, this is most difficult to understand. Put off by numbers, I’m trying to write about statistical disputes. My younger colleagues studied DNA in school, but most of them are in as much trouble with this information as I am.

“And if the press doesn’t understand it and is confused, how is the jury ever going to understand?” asked professor Raeder.

We’d prefer to be riveted by the testimony or write about Marcia Clark. But it’s DNA and statistics that will probably play a much bigger part in determining Simpson’s fate.