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Federal and state judges across the country are increasingly allowing a new test that detects only male DNA to be admitted as evidence in criminal cases. The test, called “Y-STR DNA,” detects the Y chromosome, which only men have, allowing a small amount of male DNA to be detected when it is mixed with a large amount of female DNA. It is most often used in rape cases, where the DNA samples may be difficult to separate. “Y-STR DNA can be an extraordinary technology,” said Nina Morrison, a staff attorney at the Innocence Project in New York. “It’s unparalleled in its ability to identify semen in rapes, because it can get the different [DNA] readings.” But Y-STR has its critics. In Michigan, Washtenaw County Assistant Public Defender Laura Graham argued against allowing Y-STR evidence into a murder trial, saying it was statistically unreliable. “It’s a test that only identifies the paternal side of someone’s DNA, so you basically have half of a DNA test,” Graham said. “You couldn’t use that test to make them pay child support. How could you possibly rely on this to convict someone beyond a reasonable doubt?” Morrison noted that the new DNA test pales in comparison to a traditional one, because it is only detecting one chromosome. While the common test can narrow down a reading to one person, Y-STR is not as accurate, and therefore better at including or excluding a person rather than pinpointing a suspect. The Runnion case In the high-profile murder case of a 5-year-old California girl, Samantha Runnion, the judge allowed Y-STR DNA evidence to be admitted over the strong objections of defense counsel. Camille Hill, Orange County, Calif., senior deputy district attorney, said the Feb. 15 ruling should pave the way still further for the test’s use in similar criminal cases across the country. In the Runnion case, Superior Court Judge William Froeberg ruled that the Y-STR procedures were “reliable and generally accepted in the scientific community.” Froeberg said further that “it also appears to the court that there have been no sister state or federal court cases that have rejected the use of DNA or Y-STR analysis.” People v. Avila, No. 02CF1862 (Orange Co., Calif., Super. Ct.). Orange County Deputy Public Defender Philip Zalewski, who represented defendant Alejandro Avila, did not return calls seeking comment. Dr. Laurence Mueller, a lead expert witness for the defense who testified against the use of Y-STR DNA in the case, also did not return calls or e-mails. Avila was convicted of murder, kidnapping and sexual assault last month, and received the death penalty last week. In addition to testing semen in traditional rape cases, Y-STR has several applications, including fingernail scrapings where the DNA samples are difficult to separate, rape cases where the male is vasectomized and paternity testing. However, a full Y-STR reading could identify one out of 2,000 men at most, whereas a traditional DNA test, or autosomal STR test, identifies a person with the accuracy of about one out of a trillion. Thus, Y-STR is generally used to exclude a suspect, not specifically to identify one, and has become useful in proving a person’s innocence. In 2004, Morrison and the Innocence Project were working on a case to clear Wilton Dedge, who was convicted in 1982 of sexual battery, aggravated battery and burglary in Florida. Florida v. Dedge, 873 So. 2d 338 (Fla. 5th Dist. Ct. App. 2004). Morrison found a semen sample recovered from the rape kit, but the female DNA was overwhelming the male DNA in an autosomal test. She tried a Y-STR, and the results excluded Dedge as the perpetrator. He was released from jail in late 2004 after 22 years. But Morrison has not used Y-STR in another case, and cautions other attorneys against relying on it too heavily. “The danger is that it is not very discriminating, especially in a degraded sample,” she said. “A client might well be absolutely innocent, but could share those markers just by chance.”

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