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you are here: DentalPlans.com > Dental Health Articles > HealthnewsDigest.com > IMMs Caskey Developed DNA Technique Feds Use to ID Americas Most Wanted
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Updated: 6/12/2007 2:06:43 PM |
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(HealthNewsDigest.com) - HOUSTON — When C. Thomas Caskey, M.D., embarked on a career in genetics research after graduating from the Duke University Medical School in 1963, he didn’t expect to testify at a Hell’s Angels trial or to tangle with future members of the O.J. Simpson “Dream Team” of defense lawyers.
But, Caskey – who now heads the Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM), a part of The University of Texas Health Science Center at Houston – did that and more that included pioneering a DNA fingerprinting technique used by the FBI.
Houston’s original DNA crime fighters were reunited at a Health Access Texas award luncheon May 23 honoring Dr. Thomas Caskey. In 1988, Caskey teamed up with then assistant district attorney Rusty Hardin to win a conviction in the first Texas criminal case in which DNA evidence was admitted. Left to right are: Caskey, Hardin, and Caskey’s daughter, Caroline. (Photo by Rob Cahill)
Caskey testified at the first criminal case in Texas in which DNA was used to place a suspect at a crime scene. This was an application of genetic research that no one saw coming when Caskey was training to be an internist.
Caskey, who at the time directed the molecular genetics program at the Baylor College of Medicine, also developed a DNA identification technique called short tandem repeat or STR that is today’s gold standard. The FBI converted its DNA database to the STR standard. Other laboratories use it, too.
“I didn’t intend to be a forensic scientist but my disease discovery research offered the opportunity,” said Caskey, who in 1971 moved his family to Houston from his job at the National Institutes of Health in Bethesda, Maryland.
To researchers, Caskey is the scientist who discovered 12 disease-causing genes and proved the universality of the genetic code. He also is known to the business world for senior positions at Merck Research Laboratories as well as Cogene Biotech Ventures and Cogene Ventures.
To the public, Caskey is the expert witness who helped authorities, prosecute rapists, murderers and other felons, including several suspects represented by “Dream Team” attorneys Barry Scheck and Peter Neufeld. Ironically, two years later, Scheck and Neufeld would set up the “Innocence Project” and use DNA evidence to free prisoners. “I’m glad they saw the value of DNA identification testing,” he said.
Caskey’s involvement in DNA fingerprinting started in the late 1980s in Houston with a call from then assistant district attorney Rusty Hardin who was trying to halt a serial rapist preying on elderly women. DNA had been used in England to solve the rape-strangulations of two 15-year-old schoolgirls but had not yet caught on in the United States, Hardin said.
Hardin needed someone to connect a semen stain from the mattress of a 74-year-old victim to a suspect. Not surprisingly, the prosecutor was referred to Caskey at Baylor.
Hardin, now a prominent defense attorney, said it took less than three hours for Caskey to explain how DNA fingerprinting works. The suspect got life and remains in a state prison. Texas got its first DNA-related rape conviction.
Hardin recalled Caskey telling a defense attorney during cross examination, “I’m sorry. You’re just going to have to start asking better questions.”
“I had never been in a courtroom before,” said Caskey, who edits the Annual Review of Medicine. “Defense attorneys were trying to keep DNA out and I was trying to get it in. They tried everything to discredit me. I had to learn how to control my temperament.”
Caskey testified at the landmark DNA criminal trial “United States v. Yee” at a federal courthouse in Toledo, Ohio, during which Scheck and Neufeld mounted a full-scale attack on DNA testing. Despite their protests, the DNA evidence was admitted in the case involving crime scene blood and a motorcycle gang murder. “A bullet ricocheted, struck a suspect, thus leaving blood at the crime scene,” he said.
At a hearing, Caskey was admonished by a judge who didn’t want to hear another number on the statistical probability of the DNA coming from a different person. “I said the findings were very, very, very, very, very, very, very, very significant. Each very stood for a logarithm. The jury got the point,” he said.
It was during this time Caskey’s laboratory at Baylor came up with a new DNA identification technique that required only small amounts of DNA, could be processed quickly and, most importantly, could be automated. His test focused on the one tenth of one percent of DNA that varies from person to person and involved a type of variation called STR which looks something like this:
C A T A C A T A C A T A C A T A C A T A.
Each letter stands for one of four bases in DNA, and there are more than three billion of these letters strung together in each strand of DNA.
By comparing STRs at different locations along a DNA strand, Caskey could establish a match with a high degree of certainty. For example, match repeats at one location and the odds of the DNA coming from someone else are one in 25. Match a second location and the odds climb. Match STRs at 13 locations and the odds of a sample being from someone else are in the billions.
This STR identification technique stemmed from Caskey’s work with “triple repeats” - a genetic variation he linked to a form of mental retardation called Fragile X Syndrome and a type of muscular dystrophy named myotonic dystrophy. “It was this disease discovery which led to the forensic application,” he said.
As of September 2004, the large database of DNA evidence maintained by the FBI has provided more than 17,000 matches and assisted in more than 20,000 investigations.
“A lot of criminals are repeaters,” he said. “You get the DNA of a shoplifter in a database. You may be able to use it if he is arrested again for something more serious. Seventy percent of your cold cases in England are solved by searching DNA databanks.”
Thanks to advances in technology, scientists can now make a match with a single molecule of DNA, although most rape kits and blood splatters contain hundreds of thousands of DNA molecules, Caskey said.
Caskey isn’t the only one in his family interested in clinical genetics. His wife, Peggy, operated a facility called Labs for Genetic Services and his daughter, Caroline Caskey, manages a DNA testing center in Houston called IDENTIGENE which uses her father’s DNA identification technique.
Caroline describes her father as a “visionary” when it comes to using science to help people “He has a good idea of what has value. For example, in law enforcement, DNA fingerprinting is considered the most important tool in the last half century,” she said.
Not limited to crime scene investigations, Caskey’s DNA identification technique is also used to identify catastrophe victims and to establish the paternity of children, she said.
“If you’re alert, you can suddenly see an application to something that someone didn’t think of,” said Carolyn’s father, whose discoveries also include the genes responsible for colon cancer, obesity and macular degeneration. “Scientists have to be the ultimate optimists. We get beaten down often by a lack of our full knowledge of nature.”
Joining UT-Houston in 2006, Caskey is the director and CEO of the IMM, a research institute that seeks to investigate the cause of human diseases at the cellular and molecular levels using DNA and protein technologies to elucidate disease mechanisms.
When he’s not recruiting leading scientists for the IMM, Caskey (called “Captain Tom” by a grandson) can be found behind the wheel of a sailboat navigating the waters of Galveston Bay.
Gazing into his crystal ball about future applications of DNA fingerprinting, Caskey said DNA may one day be used to determine an individual’s predisposition to a life of violence. “It could also be used to determine what part of the world a person hails from and very importantly our risk of disease. The latter opens an entirely new medical strategy - disease prevention,” he said.
www.HealthNewsDigest.com
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© 2007 HealthnewsDigest.com
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