Blood on a sock retrieved from O. J Simpson's bedroom and on the gate behind Nicole Brown Simpson's home did not contain a preservative, but only some vague and inconclusive hints of one, a scientist from the Federal Bureau of Investigation testified today at Mr. Simpson's trial.
Defense lawyers called the F.B.I. special agent, Roger Martz, to buttress their claims that corrupt police officers removed the Simpsons' blood from test tubes containing an anti-coagulating substance used in laboratories, EDTA, and sprinkled it on the sock and gate.
DNA tests have all but proved that the blood on the sock was Mrs. Simpson's, and that the blood smeared on the gate matched Mr. Simpson's. But Mr. Martz said there was no proof that the chemical on the two exhibits was EDTA and even if it were, that it was not of the concentration found in preserved blood.
"Everyone is saying that I found EDTA, but I am not saying that," said Mr. Martz, chief of the F.B.I.'s chemistry toxicology unit, with a hint of frustration. "I was asked to determine whether those blood stains came from preserved blood. Those blood stains did not come from preserved blood."
Mr. Simpson's lawyers had to call Mr. Martz because he conducted the experiments about which Dr. Frederic Rieders, an expert for the defense, testified on Monday. Although Mr. Martz technically was one of their own, from the outset Mr. Simpson's lawyers attacked him.
Mr. Martz conceded to Robert Blasier, a lawyer for Mr. Simpson, that blood found on the sock and the gate shared some of the physical properties and molecular characteristics of EDTA. In highly technical language that left even the lawyers tripping over their tongues, he said the blood samples "responded like EDTA responded" and "was consistent with the presence of EDTA."
Analyzing Mr. Martz's data on Monday, Dr. Rieders said the two blood samples did contain EDTA. But Mr. Martz said Dr. Rieders had jumped to conclusions in what he called a "very dangerous" fashion. While one test revealed some of the same ions as EDTA, he said, two others precluded its presence.
"It is not appropriate to identify EDTA based on the data I have provided for the sock and the gate," he testified.
The police have said they initially overlooked that blood smear on the gate, collecting it several weeks after Mrs. Simpson and Ronald L. Goldman were killed. Defense lawyers say the police planted it after the fact. And on the sock, they say, unidentified police officers smeared blood taken from Mrs. Simpson during her autopsy.
Examined by Deputy District Attorney Marcia Clark, Mr. Martz distanced himself still further from Dr. Rieders. He offered a bar graph comparing the number of ions associated with EDTA that were found in samples of the Simpsons' blood taken from the test tubes to those found in blood samples from the gate and sock. Those taken from the test tubes resembled orange skyscrapers; those from the gate and sock looked like empty city blocks.
Mr. Martz also restated that tests of his own blood showed the possible presence of EDTA, a preservative used in breakfast cereal, mayonnaise and other foods, in the same trace amounts as on the gate and sock. But what looks like EDTA, he said, could just as easily be a number of similar chemical compounds, or contamination from the testing instrument.
"It's only logical to assume that if a person is eating EDTA, some of it will be in their blood," he said. "The question is how much. I don't think anyone knows today."