-------------------- N E W S R E L E A S E -------------------- Auburn University - University Relations (334) 844-9999 ---------------------------------------------------------------- 4/7/95 Mitch Emmons AU EXPERTS CONFIRM VALIDITY OF DNA TESTS AS COURT EVIDENCE AUBURN -- The results from DNA testing, soon to be one of the most hotly debated subjects in the O.J. Simpson murder trial, are valid evidence in criminal cases if the tests are done properly, Auburn University scientists say. The test is considered up to 99.99 percent reliable. "If testing is done carefully and a good sample is used, the results are almost irrefutable as evidence," says Curtis Bird, an associate professor in the Department of Pathobiology. "But I think anyone who would base a decision in a criminal case on a single piece of evidence is foolish." DNA tests were conducted on samples of Simpson's blood and hair in an effort to match them with specimens found at the scene where his ex-wife, Nicole Brown Simpson, and Ronald Goldman were found stabbed to death June 12. The results will be used as evidence against Simpson, who is on trial for the double murders. Jurors will decide whether Simpson's DNA "fingerprint" put him at the scene of the crime. There is also the question of whether the blood found on and in Simpson's Ford Bronco or on the glove found on the grounds of his West Los Angeles estate can be identified as that of one or both of the victims. DNA -- short for deoxyribonucleic acid -- is a complex, two-stranded molecule wound into a double helix that makes up the chromosomes of every living cell. Each person's DNA is a unique sequence that serves as a blueprint for all inherited traits. By chemically extracting DNA from blood, semen, skin, saliva or hair follicles found at a crime scene, forensic scientists can say within a certain range of probability whether it matches DNA taken from the accused. The use of DNA as evidence in court, introduced in 1986, is controversial. DNA has been ruled inadmissible in criminal cases in six states and the District of Columbia because the distinctions it shows are based on probability instead of certainty. Marie Wooten, an associate professor in the Department of Zoology and Wildlife Science, says DNA testing is the best method available, "but it is not fail-safe." "It should not be the only piece of evidence in judging someone's innocence or guilt," she said. DNA is analyzed in scientific research for a variety of purposes, from identifying species of various organisms to forming disease diagnosis. Bird said DNA testing is similar to blood typing, but is much more accurate. It compares DNA patterns in the test example against characteristics found in a known base or marker. "Instead of looking just at compared samples, DNA (testing) looks at individual characteristics," he said. "Every individual will have a unique banding pattern," said Kim Norgren, a research associate in the Department of Fisheries and Allied Aquacultures. DNA is as individual as a person's fingerprint, says Carlos Rabren, director of the Alabama Forensic Science Lab on the Auburn campus. Rabren said DNA testing has become an effective tool in criminal investigation -- particularly with violent crimes -- during the past decade. It is used not only to establish probable guilt, but in many cases to prove innocence. But he agreed that to obtain useful evidence in criminal cases, testing procedures must be properly conducted and proven. Markers used for DNA comparisons in criminal investigations are statistically based on large segments of a given population. In most tests, four markers are examined, said Rabren. "We run population bases on black and white races (within a region)," he says. "This gives us a low enough frequency in a population where it is statistically reliable and gives the defense and the prosecution an idea of whether the person is or is not the correct defendant. "It can show, for example, that only one out of two million individuals in that particular base could have the particular DNA traits identified by those four markers." When added to other aspects of the case, Rabren says the DNA evidence is reliable. "That's statistically significant, particularly if you can place the defendant in the time-frame at the vicinity of the crime, and particularly if there is a motive for the crime," he says. The scientists agree that the more markers used in making comparisons, the more accurate the outcome. But if proper procedures are followed, the test results are valid. "It is possible that in a given set of comparisons, one individual's DNA structure could match another," Bird said. "But the chances are remote that both of those persons would be suspect in a criminal case at the same time." ------ Developed in England during the 1980s, DNA analysis is done in two ways. RFLP (restriction fragment length polymorphism) is the more discriminating analysis, but it requires more genetic material. Using this method, pieces of DNA, say from a dime-size blood stain, are illuminated with radioactivity and captured on X-ray film as dark bands. If two DNA samples share a pattern of bands, they are considered a virtual match. With RFLP the chances of a second person having an identical pattern can be one in tens of millions. Another test, called PCR (polymerase chain reaction) can be conducted on blood and tissue samples as small as the head of a pin, but it is less conclusive. PCR has been described by forensic scientists as molecular Xeroxing because individual genes, too small to be detected by themselves, are replicated millions of times in the laboratory and then compared for certain common chemical sequences. PCR, shown as a series of blue dots, can only single out the one person in 800 to 4,000 with a particular pattern. # # # april95:dna CONTACTS: Bird, 334/844-4690; Wooten, 334/844-9245; Norgren, 334/844-4085; and Rabren, 334/887-7001.