A quantitative comparison analysis of diatoms in the lung tissues and the drowning medium as an indicator of drowning

• We introduced the ratio of diatom numbers in the lung tissues to the drowning medium for forensic diatom test.
• We used the microwave digestion - vacuum filtration - automated scanning electron microscopy method to make the comparisons.
• The proportion of L/D ratio >1 in the drowning group is much higher than that in the postmortem immersion group.
• The drowning specificity of L/D ratio >1 is 0.96 and that of L/D ratio >2 is 1.00.

The presence of diatoms in the lung tissues, internal organs and bone marrow is considered as the supportive evidence in the diagnosis of death by drowning. Generally, the diatoms detected in the lung tissues are regarded as insignificant since these diatoms can be detected in the lung tissues of the postmortem immersion bodies. In this study, we analyzed the relationships between the numbers of the diatoms in the lung tissues and the drowning medium. We made a comparison analysis between the diatoms in the lung tissues and the drowning medium using the ratio of diatom numbers in both samples (L/D ratio), utilizing Microwave Digestion - Vacuum Filtration - Automated Scanning Electron Microscopy method. Our data indicate that the L/D ratios in victims of the drowning group were higher than the postmortem immersion group. A higher L/D ratio provides valuable information about the cause of death in drowning victims. Quantitative diatom analysis in the lung tissues, especially combined with the diatom analysis of the drowning medium, provides supportive evidence in determining if a body recovered in water was due to drowning or not.