Assessment of diatom composition at several locations along Tebrau Straits for assigning scene of drowning

Abstract

The use of diatoms for investigation of drowning death cases has been suggested in the literature. This study designates the assemblages of diatoms at different stations along the Tebrau Straits to establish diatomological mapping as a forensic measure to determine the site of drowning based on association of diatom assemblages recovered from the organ samples with that of the Straits. In each station, water samples from 3 substations (200 m from the shore), separated by a distance of 500 m apart were collected at 2 m depth using a Horizontal Van Dorn sampler. Replicating the same procedure, water samples from 5 different stations distanced by about 20 km from one another, along the Johor Straits were sampled during March-April 2015. To study the recoverability of diatoms from 13 real forensic cases, ranging between 9 months – 4 years, samples of organs (livers, lungs and kidneys) supplied by the pathologist were analyzed. The samples were processed using acid digestion technique and taxonomic identification of diatoms with their percentage assemblages were analyzed under light microscope. A total of 26 genera found from seawater samples were identified. The percentages assemblage of diatoms varied among the different sampling stations and hence, may be useful for distinguishing the stations. While diatoms remained recoverable in lungs and kidneys in majority of suspected drowning cases, the same was not observed in livers. The fact that diatoms were not observed in 3 later (11-12 months) cases, inferring the cause of death due to drowning may prove inconclusive.