Crime Lab Breakthrough Instrumental in HIV Infection Cases

March 01, 2011 (Press-News.org) Over the past few years, forensic advances have categorically changed the way major crimes, particularly sex crimes, are investigated and prosecuted in America. Modern forensic evidence has exonerated falsely accused defendants, increased credibility in the courtroom, and led to innumerable convictions that may not have otherwise been secured.

New forensic breakthroughs are constantly on the horizon. One in particular could have major implications for those cases involving the intentional transmission of HIV, a crime that, until recently, faced severe evidentiary challenges. Research now allows scientists to establish the direction of HIV transmission, thus allowing reconstruction of the infection events.

HIV Infection Crimes

Most of us are familiar, at least generally, with the elements of the most heavily prosecuted crimes, like robbery or murder. But a conviction for infecting another with HIV is another story. Criminal charges based on HIV infection are still developing, and to further complicate matters, laws vary from state to state throughout the country. As of the end of 2008, 36 states had prosecuted HIV positive defendants for criminal transmission or HIV exposure.

A good way to start dissipating the confusion is to look at the different types of transmission that can take place. Most common is accidental transmission, such as when the person transmitting was unaware that they had the virus (some argue that when a condom is used during sex but it fails in some way, the infection is accidental, even if the person transmitting knew their HIV status). Most jurisdictions do not criminalize accidental transmission.

Reckless transmission is next in severity; an example would be when an HIV positive person fails to inform a negative person of the risk and then infects their partner as part of the pursuit of sexual gratification. Intentional transmission is of course the most criminally serious; this may occur, for example, when an HIV positive person has sex for the primary purpose of transmitting the virus to their partner.

Obvious issues arise in proving HIV infection cases. Was there full disclosure from the positive partner? Consent? What exactly was the transmitter's intent? And, until recently, evidence showing the definite source of the accuser's HIV was hard to come by. Disclosure, consent, and intent, like many common issues that arise in a variety of criminal cases, are often matters of witness credibility, and likely to remain that way. Proving the source of a victim's HIV infection, however, will soon be easier than ever before.

The New Scientific Method Used to Solve Sex Crimes

A new paper published in Proceedings of the National Academy of Sciences is the first case study of its kind to establish the direction of HIV transmission through scientific evidence. Using what researchers call a "phylogenetic approach," the history of how viruses evolved in different individuals can be tracked and provide "evolutionary forensics" showing who transmitted the virus to whom.

This HIV analysis is not as simple as DNA screening used to match a blood or hair sample with an individual; in those who are infected, there is not only one strain but a population of strains, as HIV mutates all the time. But, researchers were able to work out the complications. According to study coauthor Mike Metzker of Baylor College of Medicine, researchers could trace their way back to likely "common ancestor" viral strains, because in each individual "there is a genetic bottleneck in which only one or two viruses get transmitted to the recipient" at the point of transmission.

In two criminal cases cited in the study (State of Texas v. Philippe Padieu and State of Washington v. Anthony Eugene Whitfield), Metzker and his colleagues isolated and sequenced two gene regions on virus samples found in blood samples taken from the accused, the victims, and other HIV positive individuals living nearby (the samples were blinded, so the researchers had no information about whether samples came from the accused, the victims, or others--by adding samples from individuals not involved in the cases and blinding all samples, the integrity of the testing was maintained).

After performing a phylogenetic analysis on the blinded samples, researchers were able to determine which individual was most likely to have infected others in the group. When combined with other evidence, the analysis contributed to the 2009 conviction of Padieu for six counts of aggravated assault with a deadly weapon (the weapon being HIV) and the 2004 conviction of Whitfield (for 17 counts of first-degree assault).

The Future

Now, researchers have shown that they can establish the direction of transmission of HIV in criminal cases involving men who intentionally infected women partners during unprotected sex. Their findings will likely be expanded, refined, and applied to additional types of cases.

The new scientific procedure will likely result in better evidence for HIV infection cases but the science comes with a word of caution: establishing the direction of HIV transmission does not speak to issues of disclosure, consent, or assumption of the risk. While the new study is a tremendous breakthrough, it should be viewed as exactly what it is: an important improvement in one piece of the complicated puzzle that is an HIV infection case.

Article provided by Roberts Law Group PLLC
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