The Diagnostic Value of the Diatom Test for Drowning, I. Utility: A Retrospective Analysis of 771 Cases of Drowning in Ontario, Canada

Abstract

The utility and validity of the diatom test for drowning was studied using a retrospective analysis of 771 cases of drowning mostly from Ontario, Canada, over the period 1977 to 1993. In this article (part one), the utility of the test was assessed using an analysis of test outcomes. In the companion article (part two), the validity of the test was assessed by analyzing the relationship between test outcome and characteristics of diatoms in the bone marrow and samples of putative drowning medium. In the present study, freshwater drownings accounted for 738 of the cases and 33 cases were drownings in bathtubs, pools, or toilets. Diatoms were recovered from the femoral bone marrow of 205 cases (28%) of freshwater drowning and four cases (12%) of domestic water drowning. There was a monthly variation in the frequency of positive test outcomes that could not be explained by seasonal differences in the total number of drownings. However, the monthly variation was strongly correlated with the periodic cycle of diatom blooms that occurs in freshwater. Positive diatom tests were characterized by a limited number of distinctive diatom species per case, and a restricted quantity and size range of diatom frustules. These results indicate that the diatom test for drowning will identify approximately one in three victims of freshwater drowning and may be useful in the assessment of deaths occurring in bathtubs. The correlation of the outcome of the diatom test for drowning with diatom blooms provides further evidence for the reliability of the test.

Role of Diatoms in the World of Forensic Science

“…Again, if specific types of diatoms recovered from the marrow can be matched with those found at the suspected drowning site, the results might implicate a particular locale of submersion and help identify the death scene, which in turn could lead to additional forensic evidence. The presence of diatoms can also corroborate investigative evidence in making accident determinations [37,45].…”

“…Electron or dark phase microscopy is currently the main methods used for analysis. These allow for more detailed imaging than simple light microscopy [45,46].…”

“…With an occurrence of less than one third, the majority of drowning cases do not benefit from this method [45] have suggested three chief reasons for the low instances of positive test results.…”

“…This leads to a decreased volume of inhaled water and a lessened window of time where the circulatory system can embolize the diatom-containing medium [3,45,47].…”

“…Finally, there is a relatively low volume of blood circulating to and through the bone and bone marrow [45]. This fact makes the investigation of other major dosed organs all the more important.…”