DNA Identification in Mass Fatality Incidents
Fragmented Remains
The remains of mass disaster victims may be commingled, which can result in mixed DNA profiles. In a situation of scattered, degraded, or fragmented remains, statistical sampling models should be used that increase the confidence of the DNA-based identification. In the WTC identification effort, for example, OCME scientists, attempting to find a portion of a sample that was not mixed, often returned to the original sample (if it was available) and attempted to reextract and reanalyze the DNA. It is important to keep in mind, however, that although well-established statistical analyses for mixtures can be applied, these result in reduced likelihood ratios that make meeting the identification threshold more difficult. Therefore, additional testing with alternative markers may be needed.
In theory, fragmented samples yielding partial DNA profiles could be associated based on their location at the disaster site. Grid coordinates, if available, might allow samples with overlapping partial profiles to be identified, particularly if the goal is to identify every human remain rather than every victim. However, even if the goal is to identify every victim, grid-coordinate methods may prove useful. Moreover, with appropriately conservative statistical approaches, partial DNA profiles from different remains may be combined to generate a composite "virtual" profile derived from a single victim.
