The use of DNA as evidence in criminal trials is now a well accepted practice, but such was not always the case. A Houston doctor played a leading role in educating judges and juries about the rock solid facts of DNA, and along the way discovered a new way to identify DNA. Houston Public Radio’s Rod Rice reports.
In the days before DNA was a routine factor at trial Dr. C Thomas Caskey, the Director of the Institute of Molecular Medicine at UT Houston, was often called upon to testify about its accuracy as an identification tool. He says he had to testify twice, first before the judge to make the case for allowing DNA evidence into the trial and then before the jury at trial. In those days DNA was used primarily by prosecutors to prove guilt. And the testimony could get technical. At one early trial a judge said no one could use numbers during their testimony or they’d be tossed out of the courtroom.
“So the defense lawyer tried to get you to say a number, so he said Dr. Caskey how significant is this data that links the evidence with the person. I said very, very, very, very, and I went through eight of them and then I said significant. And, ah, of course it was enough to persuade the jury and I didn’t have to use a number.”
This forensic work was a sideline for Dr. Caskey. His main work was in molecular medicine and successes there lead to the development of a new DNA identification technique.
“Now the common thread between these discoveries were these simple DNA repeats which were expandable and highly variable person to person. And it was sort of an “aha” moment after we made the second discovery that this technology could be used to identify the difference between individuals not just disease.”
This method allowed information to be entered into a computer forming data bases. It was fast, accurate and automated. However, Dr. Caskey says courts in this country were inclined to stick with the older technology.
“When suddenly the UK looked at our technology and said this is a winner and we adapt it. And so it was the pressure from the United Kingdom of their adapting our technology that really pushed the issue I think in the United States that FBI had to revamp their program and went with our system.”
A company that made DNA sequencing instruments licensed this new technology, known as STR, so that anyone buying their machine was licensed to use the STR technology. This produced licensing fees for Dr. Caskey.
“That fee which I donated the medical school now supports six MD PhD students, so it’s been very, very rewarding. Crime really does pay.”