If life were a movie, a paper published in this week's edition of Nature magazinewould have saved the day for six prisoners being held in a Libyan jail. Of course, it’s not and the future of one Palestinian and five Bulgarian medical workers hangs in the balance.

The paper is an analysis of HIV particles taken from children infected with the virus while they were in a hospital in Benghazi, Libya. According to the researchers, the paper provides a firm alibi for the medical workers, all of whom are accused of intentionally infecting the children.

A little back-story is needed here. In 1998, HIV infections started appearing in children who were staying in the hospital. Within a year the numbers had reached more than 400. The hospital had an outbreak of HIV on its hands. While the World Health Organization believed the problem was sanitation in the hospital, local officials disagreed. A group of medical staff from the hospital was arrested and charged with, among other crimes, intentionally infecting the children with HIV. The early stages of the trial were complicated, with accusations of torture and conspiracies, but by the time it shook down, what was left were six foreign medical workers standing accused.

The situation was rapidly muddied. The court requested an independent analysis of the situation, which was handled by Dr. Luc Montagnier from the Pasteur Institute in France. Montagnier is best known as the co-discoverer of HIV, and is considered one of the leaders in the field of AIDS research. His report concluded there was no evidence to suggest the foreign workers were responsible for causing the infections. However, the court rejected Montagnier’s report, and the results weren’t included in the trial proceedings. A second report was produced by Libyan scientists, which refuted Montagnier’s evidence. This provided the key for the whole prosecution case. In 2004, the six accused were found guilty and sentenced to death by firing squad.

International pressure was raised, and a retrial ordered. That trial wrapped up in November, with a verdict due on Dec. 19.

So now we get to this new paper. Unlike the two previous expert reports, which both looked at possible routes of infection, this paper examines the virus itself. It’s a subject called molecular epidemiology, and relies on the fact viruses mutate and evolve. In a nutshell, every time a virus moves from one person to another it changes slightly. If you look at a group of virus isolates from an outbreak, you can estimate how long it’s been since they all shared a common ancestor. In this case, the researchers are confident that the last time any of the HIV isolates they examined shared a common ancestor was at the latest 1996, two years before the foreign medical workers arrived at the hospital in Libya.

And, from my conversations with Dr. Oliver Pybus, one of the researchers involved in the analysis, this should be enough to exonerate these six individuals. He feels it would be almost impossible to fake the spread of the virus, even professional molecular epidemiologists would find it a severe challenge. As well, what’s not in the paper is a comparison of this outbreak to other HIV infections. According to Pybus, this outbreak of HIV exactly mimics other situations where it’s a lack of sanitation that’s leading to the spread, for example in injection drug users.

It’s hard to tell where the story will go from here. The plight of the accused has attracted the attention of Nobel Prize winners, the American Association for the Advancement of Science and Declan Butler, a senior reporter at Nature magazine has created a site for tracking the case at the website Connotea. But at this point there’s no easy way for this evidence to be included in the current trial. Science has provided whatever information it can. The rest is up to the politicians and the lawyers.

— Pat Senson