Siliceous non-diatom microorganisms as complementary indicators in forensic investigations of drowning deaths

The diatom test remains one of the most widely applied laboratory methods in the post-mortem diagnosis of drowning. However, its value may be limited in environments with low diatom abundance or in atypical aquatic settings. We surveyed the forensic relevance of additional siliceous, non-diatom microorganisms (chrysophyte cysts and scales, freshwater sponge spicules, ebridians, and phytoliths) detectable using standard diatom preparation techniques based on our expertise in the fields of paleoecology and marine biology, as well as the experience gained from more than 1500 diatom analyses of suspected drowning cases. These silica-based remains survive conventional acid digestion and provide additional information that can complement diatom findings. Integration of these indicators into routine microscopic evaluation of diatoms supports a multi-proxy approach, improving environmental interpretation and reducing diagnostic uncertainty, especially in diatom-poor or atypical drowning environments.