Evaluation of two methods for the use of diatoms in drowning cases

In this study, we compare digestive methods used in a forensic context to extract diatoms (37 % hydrochloric acid) to a method recently described in Italian protocols for analysis of benthic diatoms for ecological assessment of surface water (hydrogen peroxide digestion). The two digestive methods were performed using 5 g of brain, lung, liver, kidney, and bone marrow taken from the bodies of 10 drowning victims recovered from three different aquatic environments (ocean, lakes, and rivers). Postmortem examination was performed on all bodies, but aquatic samples were only analyzed in two cases. Tissue digestion was equal by both methods. Hydrogen peroxide (H2O2) digestion resulted in better diatom preservation, enabling identification of nine genera in all samples examined versus three obtained using hydrochloride digestion. The ideal digestive method to provide evidence for corroboration of a diagnosis of drowning still needs to be established. However, the benthic diatoms protocol can be useful because it is less chemically hazardous to the laboratory operator and supports better diatom preservation for reliable taxonomic analysis.