Tug-of-War on DNA Continues at Simpson Trial

Struggling to wrest helpful testimony out of an experienced prosecution witness--and hampered by tough rulings from Superior Court Judge Lance A. Ito--a lawyer for O.J. Simpson focused Monday on the error rates of the laboratories that collected and tested evidence in the murder case.

Peter Neufeld, one of Simpson’s DNA legal experts, spent much of the day grilling Cellmark Diagnostics Director Robin Cotton about possible problems with the testing in the Simpson case by posing questions about the statistical basis for describing the significance of DNA “matches” and by attempting to elicit criticisms from her about the handling of evidence by the Los Angeles Police Department.

Neufeld suggested that Cellmark’s database used to make assertions about the rarity of various genetic markers is woefully small, and he reminded jurors that Cellmark had made at least two mistakes in proficiency tests--errors that the defense lawyer attempted to emphasize by confronting Cotton with the tests and displaying them for the jury. A prosecutor later responded by noting that the mistakes occurred in the late 1980s and by eliciting Cotton’s testimony that the lab has not produced incorrect results in proficiency tests since 1989.

The themes advanced Monday by Neufeld--of laboratory error and evidence contamination--are at the heart of the defense’s attempt to rebut the DNA evidence suggesting Simpson’s guilt in the June 12 murders of Nicole Brown Simpson and Ronald Lyle Goldman. Simpson has pleaded not guilty to those killings, but his legal team is confronted with an array of DNA evidence that prosecutors say links Simpson to the crimes.

In a series of startling disclosures last week, Cotton told the jury that only one of 170 million people could be expected to have the genetic markers found in a blood drop near the bodies of the victims. Simpson’s blood was consistent with that drop, she said.

And the blood on a sock discovered in Simpson’s bedroom only could have come from about one person in 6.8 billion, she said. Nicole Simpson had that rare combination of genetic markers, Cotton testified.

Neufeld began the defense response last week, and he continued it Monday with an approach that in some ways mirrored the prosecution’s presentation. As did his counterpart, Neufeld on Monday projected slides of grainy black-and-white X-ray films that appeared to match. Unlike prosecutors, however, Neufeld then elicited Cotton’s admission that those tests portrayed by the X-rays had produced false results.

Cotton insisted that some of Cellmark’s techniques had improved since the 1988 proficiency test of her lab. But she did acknowledge that Cellmark’s record was not perfect.

“This is a false match,” she said of the 1988 test. “It is an incorrect match. It was caused by laboratory error.”

Cotton, who bridled slightly at the accusatory questioning, said Cellmark had attempted to root out the problem that caused the false match in 1988, but acknowledged that the lab erred in a proficiency test the next year, once again falsely matching one of the 50 samples submitted to it for testing. Errors such as those, Neufeld suggested, undermine the statistical significance of DNA “matches” linking Simpson to the crimes.

According to defense attorneys and some eminent scientists, the true statistical significance of a “match” cannot be greater than the laboratory’s error rate, since one possible cause of the match is that the sample came from Simpson but another explanation could be that the lab made a mistake. The results from those two tests, according to Cellmark critics, suggest that the lab’s error rate may be as high as 2%.

When Deputy Dist. Atty. George Clarke was again given the chance to question Cotton, however, he turned immediately to the suggestion that Cellmark’s past errors made its analysis unreliable. Although Cellmark has not taken tests involving large numbers of samples since 1989, Cotton said the lab has been tested on approximately 406 evidence samples during those years.

“Of those 406 samples since 1989 . . . that have been tested, how many errors has the laboratory made?” Clarke asked.

“There are no false positives and no incorrect exclusions in the remainder of those samples since 1989,” she responded.

Tempers Run Short

Although Cotton chuckled and smiled often during Monday’s session--notably when Neufeld prepared a chart in which he misspelled the word proficiency --the chilly lack of rapport between her and the DNA lawyer was obvious.

Cotton rarely faced Neufeld directly, instead directing her answers to the jury. And at one point, she and Neufeld began arguing, prompting Ito to energetically intervene.

“Wait, wait, wait, wait, wait!” Ito shouted so loudly that Cotton winced, and some members of the audience jumped.

Once the lawyer and the witness were silent, Ito fumed: “First of all, you can’t talk at the same time,” he told the two. “Secondly, when I say ‘wait,’ everybody stops, including you, Dr. Cotton, including you, Mr. Neufeld.”

Both mumbled their apologies, and Neufeld resumed his cross-examination.

In contrast to the judge’s short temper, jurors arrived Monday morning in what appeared to be good spirits. In welcoming the panel back for the week, Ito remarked: “I understand we enjoyed our weekend activities. I understand one of us was unusually lucky.”

One of the jurors, a Latino man who sits in the front row of the box, grinned and tossed a baseball that he had caught during Friday night’s Dodgers game. His fellow jurors shared a laugh, and the man put the ball away as soon as Cotton was called to the stand.

As with the early part of his questioning last week, Neufeld struggled with Ito’s interpretation of the latitude that he should have in challenging Cotton’s expertise. In particular, Neufeld sought to show that some of Cellmark’s procedures did not square with recommendations by the National Research Council in its 1992 report: “DNA Technology in Forensic Science.”

That report raised questions about the effect that laboratory error could have on the reporting of DNA “matches,” and Neufeld wanted to question Cotton about her evaluation of those findings.

“Suppose the chance of a match due to two persons having the same pattern were 1 in 1 million, but the laboratory has made one error in 500 tests,” the report’s authors wrote. “The jury should be told both results; both facts are relevant to a jury’s determination. Laboratory errors happen, even in the best laboratories and even when the analyst is certain that every precaution against error was taken.”

“A high error rate,” the report adds later, “should be a matter of concern to judges and juries.”

But Neufeld was mostly unsuccessful in raising the research council findings with Cotton.

Rules of evidence require that an expert witness only be questioned about materials that he or she relied upon in forming the opinions testified to in court. And Cotton thwarted Neufeld’s attempts to question her about the research council report by saying that while she had read the report--in fact, she had a copy in her briefcase--she did not agree with portions of it and therefore did not rely on those sections.

Based on that answer, which she gave in response to several of Neufeld’s questions, Ito upheld a series of objections from prosecutor Clarke.

Frustrated, Neufeld pleaded to be allowed to approach the judge’s bench for a sidebar conference to argue his position. Ito turned him down, leaving the lawyer to struggle in front of the jury.

Outside the jury’s presence, Neufeld complained vigorously about the limits Ito placed on questioning about the report. Ito’s approach, Neufeld said, stands “the entire rule of impeaching a witness by a learned treatise on its head. That’s what’s so remarkable with this. And that’s what’s going on here.”

Frame-Up Disputed

Near the end of Monday’s session, Clarke was allowed to return to questioning Cotton, and the prosecutor and witness resumed the style of examination that earned both high praise from legal observers last week.

As was the case then, the two worked smoothly and accommodatingly. At one point Cotton ribbed the prosecutor gently, and he responded by asking her advice about how to proceed with describing a number of samples.

In response to a question from Clarke, the biochemist sternly denied defense suggestions that her laboratory would tilt its results to favor prosecutors since the prosecution paid for the test. In fact, Cotton said that in about 30% of the cases submitted to Cellmark, her staff concludes that the suspect can be excluded based on the result of DNA tests.

Although Cotton seemed more tired this week, Clarke guided her through a long series of questions intended to debunk the defense’s claims of cross-contamination of evidence samples, either through carelessness or because of a police conspiracy.

Neufeld and the rest of the defense team have suggested that samples collected from the crime scene were allowed to degrade beyond the point where they could be accurately tested. The samples, according to the defense, were then brought into contact either with other blood swatches containing Simpson’s blood or with a vial of his blood drawn by police on the day after the murders.

The result, they allege, is that DNA tests could falsely suggest Simpson’s blood was at the crime scene.

To rebut that hypothesis, Clarke raised a number of points. Among them, Cotton said that the various bloodstains from the scene of the crime contained widely varying amounts of DNA, suggesting that different factors had contributed to their deterioration.

If the items had been contaminated because of poor storage or deliberate contamination, they probably would have been more uniform in their degradation, Cotton said, because they would not have been exposed to the elements following the contamination.

For the defense theory of contamination to hold, all the original DNA from samples collected at the crime scene would have to have deteriorated by the time of testing, so that only Simpson’s genetic markers would show up in the tests. As a result, the defense has accused LAPD criminalists of allowing the blood to degrade by using improper evidence-collection techniques, including placing the samples in plastic bags when they were first gathered.

Sealed plastic bags allow moisture to accumulate, and moisture contributes to degradation, Cotton and other experts have testified.

But on Monday, Clarke asked Cotton whether putting those samples in plastic bags had benefits as well as drawbacks.

“Do plastic bags play any role in preventing cross-contamination?” he asked.

“Of course they would,” she answered with a small laugh.

“How?” Clarke continued.

“You have one sample in a plastic bag, and you have another sample in another plastic bag,” she said. “It would be hard to get material from one sample onto the next sample.”

More DNA to Come

After six days on the stand, Cotton concluded all but a small portion of her testimony Monday after a final dispute on a statistically intriguing issue regarding DNA results. Cotton had testified last week that one part of her lab’s database was based on the sampling of fewer than 250 African Americans living in Detroit.

In fact, she added Monday, a far smaller number of those people had genetic markers in all five places that were used to derive results in the Simpson case.

“Dr. Cotton,” Neufeld asked, “how many members of your African American database have been subjected to all five genetic [markers] in this case?”

Cotton requested a sheet of paper with the statistic on it, and once it was handed to her, responded: “Of all the blacks, there are only two that are across all five.”

Jurors, who seemed to take note of that issue last week, again were attentive to it Monday. Several jotted notes in their pads as Cotton described that statistically complex point, which Neufeld used as the culmination of his questioning.

Clarke then responded by asking Cotton whether there was any problem with relying on such a small sample. She said there was not, in part because of other research in the field, and she testified that Cellmark’s database had been analyzed and that no scientist had published anything questioning its reliability.

That exchange ended Cotton’s testimony on all but the one point, statistics that she will offer regarding the significance of blood mixtures found on Goldman’s shoe and inside Simpson’s car. She is expected to deliver that portion of her testimony today, and if all goes well, the jury should then begin hearing from another DNA expert, Gary Sims of the California Department of Justice.

Sims is expected to tell the panel about results of DNA tests that his laboratory performed, including some tests that subjected the Cellmark samples to further analysis and confirmed that lab’s findings.

The Department of Justice’s results, which should be introduced in the coming days, further point to Simpson as the likely source of blood found at the scene of the crimes, and they offer a far more detailed look at the probable sources of the stains inside Simpson’s Ford Bronco, prosecutors say.