Application of Diatom Analysis in the Forensic Differentiation Between Drowning and Postmortem Immersion: A Case Series from the Yamuna River, India

Background: Diatom analysis is considered one of the most important forensic techniques for the diagnosis of drowning. The present study aimed to evaluate the reliability of diatom testing in differentiating true drowning from postmortem immersion through comparative analysis of environmental water samples and biological tissues.Methods: Thirty bodies recovered from three sites along the Yamuna River at Prayagraj, India, in 2013, were examined. Water samples were processed by sedimentation and centrifugation, and biological specimens (femoral bone marrow, clavicular bone marrow or cardiac blood) by nitric acid digestion and centrifugation, followed by light-microscopic identification of diatoms.Results: Diatoms were present in all water samples. Twenty-three of the 30 cases (77%) were diatom-positive in tissue and were interpreted as consistent with drowning; seven (23%) were diatom-negative despite diatoms in the water and were interpreted as consistent with postmortem immersion. The same taxon was found in water and tissue in only 2 of the 23 positive cases. Several diatom genera, including Cyclotella, Navicula, Craticula, Aulacoseira, Fragilaria, Ulnaria and Synedra, were identified.Conclusions: The findings support diatom analysis as a valuable supportive forensic tool for distinguishing drowning from postmortem immersion in aquatic environments, although neither a positive nor a negative result is diagnostic on its own. Results should be interpreted alongside autopsy findings, environmental investigation, and other medico-legal evidence.