Crime Library: Criminal Minds and Methods

The Murder Trial of O.J. Simpson

Blood Prints By the Billions

"Population genetics theory teaches that pairs of alleles at the same locus are
statistically independent from each other if they are in equilibrium."

— Hardy-Weinberg National Research Council report

On May 1st, the prosecution called Greg Matheson, chief forensic chemist and the supervisor of the serology unit at the SID crime laboratory. He was adamant that whichever criminalist at a crime scene collected evidence was not an important issue. He also defended Mazzola's action as viewed on the videotape, claiming nothing she did would necessarily have contaminated the evidence that was being collected.

He testified that the blood drops leading away from the murder scene were found to be consistent with Simpson's blood, pointing out that only one person in 200,000 have that blood type. He also confirmed that the laboratory testing of the blood did not include DNA testing. That was to be introduced later in the trial.

Hank Goldberg for the prosecution explained to the jury, through questioning Matheson, that the possible shortfall on the vial of blood drawn from Simpson could have come about in a number of ways. Tests carried out indicated that tiny particles of blood could have stuck to gloves, laboratory equipment or the pipettes — tube like instruments used to withdraw blood from the vial — during the various forensic testing procedures.

There had been a total of 45 blood samples taken for DNA analysis from the Ford Bronco, Rockingham Avenue and South Bundy. The defense's strategy was to imply that not only was the blood identified as their client's planted at the sites by corrupt police officers, but that the tests carried out on this and other blood samples were open to doubt.

Dr. Robin Cotton
Dr. Robin Cotton

On May 8th, the prosecution called Dr. Robin Cotton, laboratory director of Cell Mark Diagnostics in Germantown, Maryland. The largest specialist unit of its kind in America, it had performed most of the DNA tests on the blood samples taken from the crime scenes.

For three days, Doctor Cotton explained the nature and function of DNA and the tests used to identify it. In essence, DNA is that part of the chromosomes that carries the information that programs an organism from its point of conception. With the exception of identical twins, no two people have identical DNA.

In determining the so-called genetic fingerprinting tests, two methods are used. One is RFLP — Restriction Fragment Length Polymorphism and the other is PCR — Polymerase Chain Reaction. This requires less blood as a sample and is quicker to perform, but is less reliable than the RFLP test.

There are three discrete steps in RFLP analysis as performed by private laboratories like Cellmark: (1) processing of DNA from the suspect and the crime scene to produce X-ray films [autorads] which indicate the lengths of the polymorphic fragments; (2) examination of the [autorads] to determine whether any sets of fragments match; and (3) if there is a match, determination of the match's statistical significance.

In her testimony on May 10th, Dr. Cotton claimed that DNA tests showed a genetic match between Simpson's blood and the bloodstains found leading away from the bodies at South Bundy. She also confirmed that tests showed that blood on the socks found in the main bedroom at Rockingham Avenue had the same genetic fingerprint as Nicole's, characteristics that matched only one in 9.7 billion Caucasians; in other words, it was her blood. She claimed that the odds that the blood found near the bodies could have come from anyone other than Simpson were about one in 170 million.

Under cross-examination, Peter Neufeld tried to challenge Cellmark's statistical calculations and suggested that its DNA database was flawed. He also suggested that if the LAPD criminalists had improperly collected and stored the evidence, so tainting it, Cellmark's testing could have produced wrong readings. The defense lawyer also claimed that Dr. Cotton's laboratory had been subject to procedural errors on a number of occasions, casting doubt on its efficiency and trustworthiness, but she stood firm and disagreed.

On May 16th, the state's second DNA witness, Gary Sims, was called to give evidence. A senior criminalist with the California Department of Justice's DNA laboratory, he was a 19-year veteran. He testified that the blood on the socks at Rockingham matched Nicole's blood. In addition, he confirmed that blood samples lifted from inside the Ford Bronco appeared to be a mixture containing the generic patterns of Simpson, Nicole and Ronald Goldman. This was the first time that evidence had been offered to suggest that samples of Goldman's blood were found inside the vehicle, which the prosecution claimed Simpson had driven to the site of the murders that night.

By May 18th, the jury was being offered statistical information on genetic-match that had reached unbelievable levels. Linking the tests from both Cellmark and the Department of Justice, the combined chance that the blood on the socks was other than Nicole Simpson had soared to the odds of one in 21 billion. However, the scientific and technical evidence was reaching levels beyond the comprehension of most people, including the jury.

Barry Scheck came back into the fight, arguing with Sims in a series of complex hypothetical questions that DNA testing could be imprecise and that often the results could be open to different interpretation. At one point Scheck's questioning was so obscure, Judge Ito asked Sims, "Do you understand the factors involved in the question?"

"About half of it," Sims replied.

That weekend, to help bolster the morale of the jury, which had been sequestered for 133 days, Judge Ito arranged for them to see a stage performance of "Miss Saigon" and take a ride on the Goodyear Blimp.

On May 23rd, the prosecution continued hammering away on the presentation of its scientific evidence, introducing a third expert witness, Renee Montgomery, a criminalist with the State Department of Justice DNA laboratory, who reviewed under questioning that the drops of blood leading away from the victims at South Bundy could all have been deposited by Simpson. The blood stains in the Ford Bronco showed a mixture that contained the DNA patterns of Nicole and Goldman. Stains on the glove found behind the Simpson home also contained the DNA patterns of Simpson, Brown and Goldman, and finally that the DNA in the blood found on a pair of socks in Simpson's bedroom matched Nicole's DNA pattern.

The final technical expert called by the prosecution was Colin Yamauchi, another LAPD criminalist, who was the first to test much of the key evidence.

Barry Scheck was back into action spending much of May 30th, needling away at numerous areas, trying to show that Yamauchi mishandled much of the evidence, failing to change gloves before handling different tests, failing to adequately document blood testing and generally not following the department's rules designed to safeguard against contaminating blood samples.

Yamauchi confirmed that at one time during testing, he inadvertently transferred blood from the Simpson vial onto his plastic gloves, and Scheck tried hard to infer that this blood may in fact have then been transferred onto the leather glove found at Simpson's home. He denied that at any time he had been part of a police conspiracy to frame Simpson for the murders.

The jury was subjected to forensic evidence examination for almost two months. In 50,000 pages of trial transcript there are 10,000 references to DNA. If most of it was above Alan Dershowitz's head, it is hard to see just how members of the jury could have absorbed it. The linking of the blood to Simpson and the victims through the crime scenes was perhaps the most crucial part of the trial, but the prosecution obviously failed to make these connections as far as the jury was concerned.

According to Armanda Cooley, the forewoman, it was, "...witness after witness, day after day... they lost us. She (Dr. Cotton) talked down to us, and when you talk down to people, you tend to lose them.... When we went on a break, everybody heaved a sigh of relief.... Colin Yamauchi was too busy trying to protect his department.... Fung and Mazzola, I think they just got caught up and were in a rush and just mishandled things, and then tried to cover it up with explanations that never added up... their techniques just started getting sloppy... it's impossible to believe that this is the first case that they had thirty or forty errors on... God knows how many people are in jail right now due to their negligence... it was the same story over and over when it came to how evidence was collected."

The days of autorads and alleles finally ended. The talk of contamination and mixing and commingling, EDTA and ions and homologous chromosomes and genetic markers, evidentiary bands, allelic frequency and fixed-bin analysis was finally put to bed.

There would be some minor skirmishes between defense witnesses and Scheck and Neufeld, mainly over the validity of the databases used by Cellmark Diagnostics and the Californian State Justice Laboratory, suggesting that they were not large enough and did not offer a comprehensive sampling of different racial groups. The prosecution had done its dash by the end of June, and it was going to be up to the jury to finally try to make some sense out the mass of seemingly incomprehensible evidence to which it had been exposed.

According to Chris Darden, he and his team had shown the jury a high wall of physical evidence: blood, hair and fiber from three separate sites, a trail of evidence as conclusive as a video tape of Simpson actually committing the murders. At South Bundy, he had left his footprints, his cap with his hairs attached to it and at least eight separate drops of his blood. At his home he had dropped a glove that matched the one he left near the bodies, and this one contained Goldman's blood. In his bedroom, his socks were splattered with Nicole's blood. In his Ford Bronco, there were samples of both Nicole's and Goldman's blood.

Testing was done at two different laboratories, under strict control, confirming beyond a shadow of a doubt that Simpson was linked to the murders. It was a compelling conclusion. Never in the history of the California legal system had so much blood and DNA evidence been collected and amassed against one defendant to prove his guilt.

Surely, common sense would lead the jury to the only logical motherboard that was driving the prosecution's hard drive. However, as the great French author and philosopher, Voltaire once observed, "Common sense is not all that common."

By July 6th, the prosecution, after presenting 58 witnesses and 488 exhibits, had rested its case, stepping back to allow the "Dream Team" to begin its attack in defense of its client. By this point in time, the prosecutors were in really deep trouble. Their star witnesses, the police investigators and technical experts, had been hijacked, bushwhacked and taken for a one-way ride. The mountain of evidence had seemingly sunk without trace and, to make matters worse, there was the glove.