Reconstruction of HIV-1 Transmission Chains for Forensic Purposes

Phylogenetic reconstruction has become a standard way to investigate and reconstruct transmission histories. The accuracy and reliability of the methods becomes a particularly critical issue when the reconstruction is performed as part of a criminal investigation. Here we report on and discuss experiences gained from phylogenetic reconstructions of 27 Swedish HIV-1 transmission chains. The police or public health authorities had requested the investigations and in many cases the results were used as evidence in court.We have established a relatively simple procedure for reliable reconstruction of transmission chains based on double sampling, direct population sequencing, and maximum-likelihood tree analysis. In 19 cases we found support for an epidemiological link between the index case and the recipient(s), whereas in 4 cases we found no such support. In the remaining cases the epidemiological questions or the results were more complex. An important limitation is that it is usually impossible to determine the direction of HIV-1 transfer or formally exclude that the subjects under investigation are indirectly, rather than directly, linked, i.e. that the virus has been transmitted via a third person. Given these limitations, we conclude that phylogenetic analysis is a very powerful tool for reconstruction of HIV-1 transmission chains for forensic as well as other purposes.