DNA typing as a strategy for resolving issues relevant to forensic toxicology

To investigate aircraft accidents, multiple postmortem biological samples o f victims are submitted to the Civil Aeromedical Institute for toxicologica l evaluation. However, depending upon the nature of a particular accident. their body components are often scattered, disintegrated, commingled, conta minated, and/or putrefied, These factors impose difficulties with victim id entification, tissue matching, and consequently authentic sample analysis a nd result interpretation. Nevertheless, these limitations can be overpowere d by DNA typing. In this regard, three situations are hereby exemplified wh ere DNA analysis was instrumental in resolving a tissue mismatching/comming ling issue, pinpointing an accessioning/analytical error, and interpreting an unusual analytical result. Biological samples from these cases were exam ined for six independently inherited genetic loci using polymerase chain re action (PCR) suitable for analyzing degraded DNA generally encountered in p utrefied/contaminated samples. In the first situation, three of five specim en bags from one accident were labeled with two different names. DNA analys is revealed that one of these bags actually had commingled specimens, origi nating from two different individuals. Therefore, the sample was excluded f rom the final toxicological evaluation. In the second situation, an unaccep table blind control result was reported in a cyanide batch analysis. By com paring DNA profiles of the batch samples with those of the known positive a nd negative blind controls, it was concluded that the error had occurred du ring the analysis instead of accessioning. Accordingly, preventive measures were taken at the analytical level. The third situation was related to the presence of atropine at toxic concentrations in the blood (318 ng/mL) and lung (727 ng/g) with its absence in the liver, spleen, and brain. DNA analy sis of the blood and liver samples exhibited their common identity, ensurin g that the submitted samples had indeed originated from one individual. The selective presence of atropine was attributed to its possible administrati on into the thoracic cavity by the emergency medical personnel at the accid ent site for resuscitation, but circulatory failure prevented its further d istribution. These examples clearly demonstrate the applicability of the PC R-based DNA typing to enhance the effectiveness of forensic toxicology oper ation.