Citation

Sonoda A, Kakizaki E, Shinkawa N, Matsuda H, Yukawa N. Forensic Sci. Int. 2022; ePub(ePub): ePub.

Copyright

(Copyright © 2022, Elsevier Publishing)

DOI

10.1016/j.forsciint.2022.111510

PMID

unavailable

Abstract

The number of diatoms detected in the kidneys and liver varies considerably when comparing various reports, but the reason remains unclear. We previously showed that the reuse of Kjeldahl flasks is susceptible to generating false positives; false-positive results were observed in 17 of 60 tested flasks, and a maximum of 290 diatoms were detected. Furthermore, these data suggested that the number of diatoms in kidney and liver tissue may be much lower than previously thought. Therefore, only new Kjeldahl flasks were used to perform diatom tests on 80 autopsy cases (drowning and non-drowning victims) in this study. When combined with the 20 cases in a previous study, a total of 100 cases were analyzed. Four grams of lung, 10-30g each of kidney and liver, 10mL of blood, and 50-100mL of water (discovery site) were examined. A large number of diatoms (n=400) were found in organs other than the lungs in only 1 of 56 cases of suspected drowning (excluding cases of suspected drowning in baths). Together with the previous 20 cases, this single case represented only 1 of 76 cases (1.3%). In closed organs and blood samples, 3 diatoms were found in 2 of 56 victims (3.6%), and 1 or 2 diatoms were found in 8 victims (14%). However, 5 diatoms were found in 1 of 10 bathtub drowning victims and 12 non-drowning victims (4.5%), and 1 or 2 diatoms were found in 6 victims (27%). Moreover, 1 or 2 diatoms were found in negative control flasks in 3 of 80 victims (3.8%). The results showed that distinguishing false-positive results is difficult when a small number of diatoms are found in the kidneys and liver. Thus, the presence of diatoms in closed organs and blood seems to be unreliable as evidence of death by drowning, at least in the water environments in our region (freshwater areas: 23-26,000 diatoms/mL, median 200 diatoms; brackish water areas: 26-1,200 diatoms/mL, median 210 diatoms; seawater area: 2-1,000 diatoms/mL, median 24 diatoms). These results also reconfirmed that the reuse of flasks is the most important cause of false positives. Conversely, the presence of a large number of diatoms in lung samples (1-850,000 diatoms/g lung tissue; median (right lung): 440 diatoms, (left lung): 320 diatoms) is very informative and is an effective diagnostic aid in many cases.

Language: en

Keywords

diatom test; drowning; false positive; fuming nitric acid; Kjeldahl flask; strong acid digestion