Simplification of Complex DNA Profiles Using Front End Cell Separation and Probabilistic Modeling

Forensic samples composed of cell populations from multiple contributors often yield DNA profiles that can be extremely challenging to interpret. This frequently results in decreased statistical strength of an individual’s association to the mixture and the loss of probative data. The approach of the current project involved selectively labeling certain cell populations in dried whole blood mixture samples with fluorescently labeled antibody probe targeting the HLA-A*02 allele, separating the mixture using Fluorescence Activated Cell Sorting (FACS) into two fractions that are enriched in A*02 positive and A*02 negative cells, and then generating DNA profiles for each fraction. Researchers then tested whether antibody labeling and cell sorting effectively reduced the complexity of the original cell mixture by analyzing STR profiles quantitatively, using the probabilistic modeling software, TrueAllele® Casework. Results showed that antibody labeling and FACS separation of target populations yielded simplified STR profiles that could be more easily interpreted using conventional procedures. Additionally, TrueAllele® analysis of STR profiles from sorted cell fractions increased statistical strength for the association of most of the original contributors interpreted from the original mixtures. (Publisher abstract modified)