THE DEVELOPMENT AND APPLICATION OF A DIATOM-BASED QUANTITATIVE RECONSTRUCTION TECHNIQUE IN FORENSIC SCIENCE

The most frequent use of diatoms in forensic science is the diagnosis of death by drowning. We use a relatively new quantitative diatom-based reconstruction technique in two recent, high-profile case studies to confirm drowning as a cause of death. Furthermore, we use the quantitative model to correlate control samples from the study area and diatoms recovered from clothing and lung to localise the site of drowning.

In Case Study 1 a body of a woman was found face down floating in a river. We collected samples for diatom analysis from sites along the length of a river, including the body recovery site to act as a control in the examination of diatom assemblages associated with lung fluid and clothing belonging to the accused. The modern analogue technique suggests that all lung and clothing samples have statistically significant similarities to control samples from shallow water habitats. The reconstructions suggest the site of drowning was the body recovery site. In Case Study 2 the body of a boy was found face down floating in a pond. The case was reopened recently, because of a suspicion that drowning had occurred in a domestic bath and the body transferred to the pond. We collected samples for diatom analysis from transects around the circumference and centre of the pond in which the deceased was found. Although it is difficult to speculate on the origin of the diatoms in the lung samples without examining a sample of water from the pond at the time of drowning, the analogue matching suggested that the majority of lung samples show a statistically significant relationship to samples from the pond, indicating that the pond was the location of drowning.

Diatoms have a number of characteristics, including their widespread occurrence, sensitivity to environmental water quality, good preservation, easy detection and prevalence in high numbers for a good statistical base for quantitative interpretations, to suggest that they have further use in forensic investigation.