DNA Process Facing Test in Rape Case

The first San Diego court test of “genetic fingerprinting” is set to begin today, pitting a prosecutor who is sold on the identification technique against a skeptical defense lawyer who claims it’s relatively untested.

The prosecutor, Deputy Dist. Atty. Michael Carpenter, wants to use the novel technique to convict a man accused of raping a Pacific Beach woman. He plans to urge a San Diego Superior Court judge to allow him to tell a jury at the upcoming rape trial how genetic fingerprinting works and why it provides such devastating evidence.

Judge William D. Mudd will preside over the hearing, expected to last a couple of weeks, while experts--in subjects such as population genetics and microbiology--duel from the stand over the technique’s reliability.

The question facing the judge is whether the technique is “generally accepted” in the scientific community.

“Genetic fingerprinting” evidence has been admitted in other California criminal cases this year, and even in San Diego County at least once before--just last week, in fact. But the evidence did not play a key role in that case, and the hearing before Mudd appears to mark the first time the technique will be challenged in county courts by an objecting defense attorney.

Although the application of genetic fingerprinting in criminal cases is novel, it has been widely used for a variety of other applications, including paternity tests.

Judges in 18 states have approved the use of the technique, and, since late summer, it has been allowed in cases in Ventura and Alameda counties. Judges in at least two states, however, have refused to allow it into court.

Genetic fingerprinting got its name, Carpenter said in legal papers filed recently, because it can be used--like a fingerprint--to identify a suspect.

But while a fingerprint can only exclude a suspect, or point merely to the likelihood of a suspect’s involvement in a crime, genetic fingerprinting can show--purportedly to probabilities of billions to one--that a particular crime involved a particular person.

Carpenter contends that tests run in this particular case show genetic patterns that point to Barrett Brooke Littleton. The prosecutor has other evidence--for example, the victim identified Littleton at a photo lineup, a live lineup and at the preliminary hearing--but nevertheless considers the tests important to his case.

“What you’re talking about is ability to get a lot closer to the truth,” Carpenter said last week.

Littleton’s defense attorney concedes that the complicated technique is scientifically remarkable. It breaks down the very essence of genetics to a pattern that closely resembles the familiar bar codes used in pricing items at a grocery store.

But public defender William D. Saunders plans to argue that the technique, although promising, has simply not yet proved reliable.

If anything, Saunders said recently, Littleton’s case involves an issue that anyone who has ever been near a courtroom can understand without fancy technology--a problem of mistaken identity.

Littleton, 44, of San Diego, is charged with two counts of rape as well as oral copulation and burglary in connection with the Sept. 14, 1988, attack on a 24-year-old woman at her Pacific Beach apartment.

Police found four stains on the victim’s comforter and also obtained vaginal swabs from her, Carpenter said in his legal papers. At first, lab technicians performed only standard blood tests, comparing the blood and saliva of the victim, her boyfriend and Littleton.

The boyfriend, technicians found, had Type O blood. Both the victim and Littleton were Type A, they said.

Further classic blood and saliva tests on the stains indicated they could have come from a relatively small segment of the population, roughly 15%, Carpenter said.

Those tests strongly suggested the likelihood of Littleton’s involvement, Carpenter said. But the prosecutor said he decided he wanted “the individual identification you can get through DNA testing”--that is, genetic fingerprinting.

DNA--or deoxyribonucleic acid--contains the chemically encoded genetic information that determines each person’s physical makeup. It is found in virtually every cell of the body and may be extracted from, among other things, blood or semen or their dried stains, vaginal swabs, hair roots and the lining of the mouth. Every person--except for identical twins--has links of DNA that are unique to him or her. Those highly variable individual links of DNA are what provide the basis for genetic fingerprinting.

Although different methods exist for testing DNA, the technique essentially involves chemically cutting it into strips, separating the fragments into bands, then lining up the DNA markers according to length so they resemble the familiar bar codes, according to scientific and legal journals.

Initial testing showed that a pattern taken from the vaginal swabs matched the pattern taken from Littleton’s blood, Carpenter’s brief said.

Further testing showed that the pattern from the vaginal swabs contained her DNA pattern, two of eight bands taken from the boyfriend’s blood and five of seven bands obtained from Littleton’s blood, the brief said.

Both the woman and Littleton are white. The chances in the Anglo population of the five bands being common to both the woman and Littleton are about 1 in 8,100, the brief said.

The degree to which a test can point to a particular person varies with the technique used and the condition of the sample, say the three major labs that do the tests.

Under ideal conditions, one of the three labs claims it can determine that the DNA print of a given individual is unique to a statistical probability of 30 billion to 1, according to a legal journal. Another lab advertises that its method can individualize to 840 million to 1.

Odds of 8,100 to 1, Carpenter said, admittedly are “not as good as one in 800 million, but (they’re) pretty good,” Carpenter said.

Saunders, however, contends that not only did the testing find that some of the DNA markers matched up with Littleton or the boyfriend or both, others bore “no resemblance to either person.”

“It makes the issue of identification a lot more complicated than if there were just two people,” he said.

“We contend there’s somebody running around who looks like Mr. Littleton who’s responsible for this rape, and we expect he would have a DNA pattern generally resembling (Littleton) because he resembles him in a general sense,” Saunders said. “It’s a classic mistaken-identity issue.”

What happened with these tests illustrates their basic problem, Saunders said. The tests rely on inadequate databases, he said, to assign the numerical frequencies that, in turn, translate into the statistical projections. Littleton’s fluid samples, for example, were compared with those from other whites, he said.

“I would be a lot more comfortable if they had a database for blue-eyed, blond-headed people (like Littleton), so they could identify which bands would be held in common by people who have blond hair and blue eyes, instead of all being lumped into a Caucasian database, whatever that is,” Saunders said.

The “bugs haven’t all been worked out,” he said. “It’s that simple.”