Coming on 20/20: The Case of Philippe Padieu

May 28, 2009 -- For the first time in Texas history and only the third time nationally, DNA sequencing was used to convict a man who knowingly exposed sexual partners to HIV, infecting at least six women.

A jury in Collin County, Texas, found Philippe Padieu, 53, guilty Wednesday on six counts of aggravated assault with a deadly weapon. Prosecutors told jurors in closing arguments that Padieu knew he was HIV-positive in the fall of 2005 but continued to have unprotected, "high-risk" sexual intercourse with multiple women, exposing them to the virus that causes AIDS.

"He's a predator," Assistant District Attorney Curtis Howard told jurors. "He's a ticking time bomb.  He's a lethal weapon."

Defense attorneys argued that Padieu was in denial, that he had no obligation to disclose his HIV status and that the sex was consensual.  "Mr. Padieu is not a predator," attorney Bennie House said. "He's a polygamist.  He likes sex."

Six of Padieu's former sexual partners tested positive for HIV and came forward to press charges.

Look for Elizabeth Vargas' full report on the case on an upcoming "20/20."

Prosecutions involving the transmission of HIV are not uncommon in the United States. But what sets Padieu's case apart is the use of phylogenetic analysis and DNA sequencing as a forensic tool. Dr. Michael Metzker, an associate professor in molecular and human genetics at Baylor College of Medicine in Houston, testified on behalf of the state. He had been hired to conduct a blind study on blood samples from each of the six victims and the defendant.

Metzker told the jury that based on the HIV strain present in the DNA of each sample, one individual stood out as being the most likely source of all of the other infections.  Prosecutors revealed that the sample belonged to Padieu.

Earlier in the six day-long trial, Padieu's doctor, Dr. Pedro Checo, an internist based in Frisco, Texas, testified that the defendant was tested for HIV in September of 2005, was informed that he was HIV-positive and was counseled about the importance of safe sex.

But six women who were intimate with Padieu after his diagnosis testified that he never disclosed his status.  Several of the victims said they raised the topic of safe sex and using protection.  His response, they said, was "I'm clean."

Philippe Padieu Told Partners: 'I'm Clean'

Although she didn't realize it until after he was arrested in 2007, one victim said she went with Padieu to the 2005 doctor's appointment when he was informed he was HIV-positive. She waited in the parking lot for him until he returned.  Then, she said he looked her straight in the eye and said he was "negative."

Another victim said she told the defendant she was having health issues and wanted to get tested for sexually transmitted diseases.  "He tried to talk her out of it," prosecutor Lisa King said in closing arguments, "[because] if she finds out she's HIV-positive, his house of cards begins to crumble."

At least 33 states now have some kind of HIV-specific law on the books.  Lacking such a statute, Texas prosecutors brought the aggravated assault charge against Padieu.

Brian Fair, a criminal law expert at Baylor Law School in Waco, said the charge fits in this case. "To be an assault, you have to intentionally know you put someone at substantial risk," Fair told ABC News. "Padieu knew he had HIV and he knew he could spread it through sexual intercourse. So now that the person or persons has HIV, it can be argued that he knowingly and recklessly intended to cause them harm and bodily injury."

Although all six victims in this case were HIV-positive, there have been cases in Texas in which the same charge has been applied and the victim tested negative.

Padieu was born in France but came to the United States with his mother, who married a U.S. citizen, when he was 10. He faces a sentence of up to 99 years in prison.