Scientists Use Virus to Trace Assault Suspect

ByLee Dye

Oct. 17, 2002 -- Janice Trahan was lying in bed alongside her young son when her ex-lover, a Louisiana physician, jammed a needle in her arm. Dr. Richard J. Schmidt had told Trahan he was giving her an injection of vitamin B-12, but she later told friends she sensed immediately that something was wrong.

Seconds after giving the injection, Schmidt fled the room.

Over the decade that she had been having the extramarital affair with Schmidt, the doctor had given her three abortions and she had a son with him. He had repeatedly threatened to harm Trahan, who worked as his nurse, if she left him for another man.

But she ended the 10 year relationship when he told her he would not leave his wife, despite the fact that she had divorced her husband. So on Aug. 4, 1994, Schmidt carried out his threat. The injection contained HIV, which causes AIDS.

In February 1999, Schmidt was convicted by a Louisiana court of attempting to murder Trahan, who is now HIV-positive, and the doctor was sentenced to 50 years of hard labor. The next year the state Court of Appeal upheld the conviction, and earlier this year the U.S. Supreme Court turned down an appeal.

Tracking a Changed Virus

And there it might have ended, except the real legacy of this tawdry affair goes far beyond a single trial. Scientific evidence that helped put Schmidt behind bars could have many other applications, including tracing pathogens released during biological warfare back to their source, or finding the source of a new virus, or even tracing food contamination back to a specific processing plant.

But perhaps the most astonishing thing of all is the fact that the evidence was even admitted into court. You see, it's based on evolution.

"Evolution biology has come full circle from being sort of suppressed by the courts, with the Scopes trial in 1925, to being sought out and used in court to try and figure out what actually happened," says David Mindell, associate professor of evolutionary biology at the University of Michigan, a key player in the Schmidt case. Mindell is coauthor of a report in the current issue of the Proceedings of the National Academy of Sciences that explains how the Schmidt evidence was developed.

It would have been easier if the HIV found in Trahan's blood could have been found to be exactly the same as the virus found in a vial of blood in the refrigerator in Schmidt's office, which was believed to be the source. That isn't possible with HIV because the virus mutates immediately upon being transmitted to another host, and it continues mutating at a very rapid rate.

So the virus found in Trahan would naturally be different from the virus in the blood in Schmidt's office because it had continued to evolve over the months, and years, between the attempted murder and the trial.

Determining if the vial of blood could indeed have been the source of the virus was not as simple as DNA testing like that used in the O. J. Simpson trial, or fingerprinting, both of which are based on finding similar patterns. To prove it, researchers had to show that the two viruses were so closely related that they came from the same family tree and shared a common ancestor.

Seeking Blood Brothers

The prosecution turned initially to Michael Metzker, an expert in molecular genetics and phylogenetic analysis (evolutionary history) of HIV at the Baylor College of Medicine in Houston. Metzker, lead author of the report in the Proceedings of the National Academy of Sciences, began piecing together the history of the evolution of the virus from Trahan and the blood found in Schmidt's office.

But to guard against any chance of contamination, or bias, the prosecution asked Mindell to conduct the same tests. David Hillis, another expert on HIV at the University of Texas, was selected to compare the results of both series of tests.

Blood was drawn from 28 AIDS patients in Louisiana to be incorporated into the test so that the researchers could compare similarities between the Trahan sample and others.

"We compared the DNA sequences" from all the samples, Mindell says, "looking for shared characters," or common traits.

"It is really like a family tree," he adds. The researchers were looking for what they call the "maximum likelihood" that each sample belonged on a particular tree. It's a painstaking process because "there are hundreds of thousands of possible trees."

They were looking for, quite literally, blood brothers. And in the end they found it. Graphics showing the DNA sequences for all the samples revealed two that "leaped out" at the researchers. After looking at the results of both research efforts, and ruling out any chance for contamination, Hillis testified that two of the samples were "closely related." So close, he said, that no two samples could be any closer.

One of the two came from Trahan. The other came from the AIDS patient whose blood was found in Schmidt's office.

Age of New Evidence

It's worth noting that the evolutionary evidence isn't what put Schmidt in the slammer. There was other circumstantial evidence, including a boast from Schmidt that he would infect his nurse with AIDS if she dropped him as a lover.

But the scientific evidence showed that Schmidt could not be ruled out as a suspect. And the two viruses were so closely related that the virus Schmidt shot into his Trahan's arm almost certainly came from the vial of blood found in his office. Thus the evolutionary history became a key in the prosecution's case. Even the expert witness for the defense ended up admitting on the stand that the two samples came from the same evolutionary tree, so they were very closely related.

That was the first, and as far as could be determined, the only time that evolutionary history has been used in a court in this country to convict a criminal. But it probably won't be the last.

Prosecutors have a new and powerful forensic tool in their hands, and that's only part of the story.

Mindell says the technique could be used to trace almost any biological pathogen, like those that could be released during biological warfare, back to its source. Investigators would need samples of what they suspect to be the source, of course.

"It doesn't mean you identify who was involved, but if you have an alleged source, or some material you suspect might be the source, this can be a powerful way to test that hypothesis," he says.

Equally important, it might rule out a suspected source, thus reducing the chances that some country will bomb the wrong suspect.

Although testing for the Schmidt trial took months, Mindell says it could be done much more quickly in the event of biological warfare.

"This could be done in a week," he says.

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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