Blood Analysis Pits Lawyers and Scientists : Debate Over Stains Enlivens Peyer Case

Several small patches of dried blood and the esoteric techniques used to decipher the blood’s genetic secrets have become a hotly disputed issue in the high-profile murder case against former CHP Officer Craig Peyer.

The prosecution hopes to use as evidence in Peyer’s upcoming trial the blood stains found on a sweat shirt and boot worn by murder victim Cara Knott--stains that prosecutors say their analyses will show are unlikely to have come from anyone other than Peyer.

But Peyer’s defense lawyers have challenged the use of the tests, questioning whether they are reliable and scientifically accepted. They are asking the court to bar the prosecution from using some of the results in Peyer’s trial.

Challenges on Rise

The dispute, which dominated pretrial proceedings in San Diego two weeks ago, appears to some experts to be part of a growing trend in which they say lawyers increasingly are challenging scientific methods for drawing distinctions between blood samples.

Some lawyers say the challenges are a good sign--an indication of increasing awareness that the tests are not infallible and can be challenged. In the past, they suggest, lawyers and juries have been insufficiently skeptical of scientific evidence.

But some forensic scientists charge that the challenges are little more than a legal game. They say their techniques are both proven and, in many cases, commonplace. They say there is no question among scientists--just among lawyers--that the tests are valid.

“It’s sufficiently common that it’s certainly a cause of concern among the forensic science community,” John Thornton, a professor of forensic science at UC Berkeley, said of recent efforts to exclude serological evidence from court cases.

“The forensic science community is being jerked around somewhat by this attack,” Thornton added in a telephone interview last week. “. . . This is a successful legal attack, but it’s not a scientific attack.”

In the Peyer case, the issue is rooted in several small blood stains found on the clothing of Knott, the 20-year-old San Diego State University student Peyer is accused of strangling and dumping off a bridge near Interstate 15 on Dec. 27.

After Peyer’s arrest, law enforcement officials took a fresh sample of his blood and had it “typed” by forensic scientists, a technique that entails conducting tests to identify distinctive characteristics in the blood known as “genetic markers.”

Since then, the scientists have begun comparing Peyer’s blood to the stains found on Knott’s clothes. They have also compared the stains to a known sample of Knott’s blood to determine whether the blood came from her.

In the case of the stain on Knott’s boot, a criminologist testified that it matched Peyer’s blood for all three markers for which he tested. Two of the three markers differed from the markers found in the analysis of Knott’s known blood.

Another lab has done a different test on the sweat-shirt stain, looking for two additional markers. The results of that test, according to court papers, “excludes the victim as a possible donor but includes the defendant.”

The San Diego district attorney’s office intends to have tests for additional markers done on the stains, Assistant Dist. Atty. James Atkins said, adding that the office decided to “exhaust the stain and test for as many markers as possible.”

“The theory is that it’s her murderer’s blood on her,” Atkins said. “. . . It’s a whodunit: Who’s blood is it? By testing as many markers as possible, we narrow the possibilities. With each marker you get, it narrows it down.”

Lawyers Against Test

The tests that Peyer’s lawyers are most aggressively contesting are tests for so-called Gamma and Kappa markers. Those markers are antigens in blood serum that come in many types. Atkins said the type of so-called Gm marker in Peyer’s blood is “very rare.”

The tests for those markers were developed in the 1960s and have been used widely in Europe since then, proponents say. But because certain reagents used in the tests were unavailable until recently, the tests have been used only since the mid-1980s in the United States.

So Peyer’s lawyers have contended in court papers that the technique falls short of the standard for scientific evidence in California courts, which requires that any procedure be generally accepted by the scientific community before the results are admissible.

Defense lawyer Robert Grimes said, “We argued in our motion that it is our belief that there are approximately four forensic labs out of hundreds in the United States that use this type of testing. We feel that that’s because it just isn’t accepted.”

Grimes and Diane Campbell, Peyer’s other lawyer, also initially challenged a second form of testing used to compare one stain to Peyer’s blood. However, they dropped that objection after pretrial testimony before Superior Court Judge Richard Huffman.

That technique, used by the San Diego Police Department, entails testing for so-called ABO antigens and for certain distinctive enzymes in the blood. The enzymes involved in the Peyer case are Phosphoglucomutase (PGM) and Esterace D (EsD).

Those enzymes and many others are known to be “polymorphic,” meaning they come in numerous types that vary within populations. So over the past 15 to 20 years, the tests to identify them have played an increasing role in blood typing.

“They’re used every day across the country,” said Thornton, the forensic scientist at UC Berkeley. “They’re practically the furniture of the consciousness of any operational crime laboratory.”

Nevertheless, Thornton and Randolph Jonakait, associate dean of New York Law School in Manhattan, said they have noticed an increasing number of challenges recently to admitting such evidence in court cases nationwide.

They said that in some recent cases, in states including California, courts have acceded to requests to bar blood-typing evidence (though experts acknowledge that such evidence is still allowed in the vast majority of cases in which it has been introduced).

Jonakait traced the trend in part to a lengthy critique of blood typing that he wrote and had published in 1982 in the Emory Law Journal. (The article has been cited extensively in papers submitted by the defense in the Peyer case.)

In that article, Jonakait argued that new methods for identifying genetic markers had put “a tremendous new tool” in the prosecution’s hand. Yet, he said, there had been few objective, scientific studies to determine whether the tests were reliable.

He said the literature did contain “proven and potential areas of unreliability in the tests’ uses.” For that reason, he argued that the tests’ results should not be admitted in court until the techniques had been rigorously studied.

“I had not seen it being challenged,” Jonakait said last week. “One of the things that has changed is that defense attorneys have become more sensitized to this being a possible issue. I think in trial courts, it’s being more and more challenged.”

Focus of Challenges

Experts say the challenges have tended to focus on several issues:

- Lawyers have questioned the applicability of tests designed for fresh blood to the kind of dried blood usually involved in criminal cases. They have wondered whether drying alters genetic markers or whether the blood is changed by the surface onto which it dries.

- They have also raised questions about the objectivity of forensic laboratories that analyze blood samples. Noting that even private labs receive most of their business from law enforcement agencies, lawyers have suggested the labs have a stake in the outcome.

- Finally, they have questioned the population surveys that have been used to determine how common an individual’s markers might be in the general population. They say the surveys are rarely based on random samples and therefore may not represent the public at large.

Forensic scientists, however, dismiss those arguments.

Moses Schanfield, laboratory director of Allotype Genetic Testing Inc., in Atlanta, said laboratories can perform accurate tests on stains of dried blood down to three microliters--the equivalent of “a fleck of blood” the size of a pinhead on the front of a jacket.

Schanfield, a pioneer in testing for Gm and Km markers in the United States, said forensic laboratories have no vested interest in a particular result.

“Our job is not to punish or convict people,” he said. “It’s to generate data.”

As for the population frequencies, Schanfield said any imprecision in the tables would “cancel out” when calculating the frequency of a combination of markers. He said the aim is broad percentages, such as under 1%, under 10% or under 50%.

Kind of Pettifoggery?

On the whole, Thornton characterized many of the challenges as a kind of pettifoggery in which lawyers quibble about such things as environmental effects, raising innumerable questions about blood deterioration in contact with materials like cloth or plaster.

“Judges being attorneys, I think that by and large they are seduced by this opinion that ‘You haven’t checked out this brand of plaster,’ ” he mused. “Or, here’s a blood stain on clothing: ‘Well, have you checked out denim? Have you checked out brocade?’ ”

Thornton contended that there is “almost universal acceptance within the scientific community concerning the validity of these markers.” He added later, “That doesn’t mean that the results of any given test are infallible. Mistakes do occur.”

He and others acknowledge that there have been documented errors in the use of blood typing, but they trace those errors to the proficiency and management of forensic labs, not to fundamental flaws in the technique.

Jonakait, however, predicted blood typing for genetic markers would eventually be eclipsed by a newer and more precise technique nicknamed DNA fingerprinting, which some people say will replace traditional fingerprinting in court cases.

The process, developed by a British geneticist in 1985, entails extracting deoxyribonucleic acid (DNA) from bodily fluids or tissue, then analyzing it for a comprehensive picture of a person’s unique genetic information.

Only two firms are reportedly offering the procedure in the United States, and few cases involving DNA fingerprinting have yet reached the courts. Even so, Jonakait speculated that that process may eventually prove more reliable than current blood typing.

Schanfield, however, said DNA fingerprinting demands a much larger stain than typing requires. He also contends that DNA is less stable and more susceptible to damage over time than the markers used in blood typing.

Asked why his office had not tried DNA fingerprinting in the Peyer case, Atkins said the process would have used up the small amount of blood stain available. On top of that, the office would have run the risk of the novel technique not being allowed in court.

How About Juries?

Oddly enough, there is little agreement on juries’ attitudes to scientific evidence.

“There’s a debate about that,” said Paul Gianelli, a professor of law at Case Western Reserve Law School in Cleveland and co-author of a text on scientific evidence. “Some people think that the jury is overawed by the evidence. There are people on the other side saying that’s not true, juries can sort this out, just as they sort out many other things.”

As for blood-typing testimony, Schanfield said, “Juries do not necessarily understand it. What a jury comes away with is, in my opinion, impressionistic.”