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Author Topic: Male DNA test yields clues in Texas criminal cases  (Read 1057 times)
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« on: January 10, 2010, 10:10:17 PM »
Male DNA test yields clues in Texas criminal cases

Published: 7:22 p.m. Sunday, Jan. 10, 2010

HOUSTON An advanced type of DNA testing that is male-specific is helping Texas law enforcement solve sexual assaults and other crimes that previously netted inconclusive results.

The Y-chromosome detection analysis is able to extend the evidence collection time from 48 hours on up to 120 hours, experts say.

It separates male DNA profiles from those belonging to females and hones in on tiny bits of saliva, skin cells, semen and other biological evidence.

In gang rapes, the male-specific test can determine the number of men involved. But it falls short in same-sex assaults and can't differentiate between male siblings.

Although the test has existed for at least eight years, some of the state's larger law enforcement crime labs have only recently become equipped to conduct their own analysis as courts have become more accepting of newer technology.

"It's not a common kind of test you use all the time; it takes a considerable amount of work to get those systems up," said John Planz, associate director of the University of North Texas Center for Human Identification in Fort Worth, which has been working to refine the testing kits.

The Texas Department of Public Safety crime lab, which handles forensic testing for various agencies across the state, including the El Paso Police Department, started conducting its own male-specific DNA tests in the middle of last year, DPS spokesman Tom Vinger said.

The Harris County Medical Examiner's Office biology lab began using the test about the same time. Since June, it has obtained positive results in 20 sexual assault cases most involving children though none of those cases has gone to trial yet.

"Everyone recognizes (this) testing will work when traditional testing doesn't," Dr. Roger Kahn, the Harris County medical examiner's forensic biology director, told the Houston Chronicle. "The number of successes is up."

In the case of a 9-year-old girl who told authorities that a male relative molested her while she slept, there were no witnesses and no semen recovered. Harris County's supervisory forensic investigator Dan Morgan said traditional DNA tests yielded inconclusive results. But testing using the new analysis found a partial DNA profile on swabs and portions of the girl's clothing that matched the suspect's.

Like a black light that causes white clothes to glow in the dark, the technology in the new test essentially makes the female DNA profile invisible and amplifies any male DNA, no matter how small, that may not have been seen before.

The male-specific DNA tests can also be used to solve crimes involving people of the opposite sex, such as burglaries or homicides that do not involve rape.

But the advanced tests only work in cases where a suspect has given a DNA sample to investigators looking at a specific crime, Kahn said.

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