Acid Digestion Method for Extraction of Diatoms in Drowning Cases: A Review

Diatoms are single celled algae and is the most found phytoplankton in water sources like rivers, lakes, pools, ponds, etc. In cases of drowning, it becomes essential to prove that the person died due to drowning. In this aspect there are basically two conditions that need to be investigated, to prove it. The point of proving that it was an ante mortem drowning helps in determining the crime committed and plays a vital role in the conviction of the accused with the appropriate punishment. In ante mortem drowning the water is swallowed by the individual and since the person is still alive this water gets absorbed and enters the blood stream. Therefore, if a person was actually drowned which resulted in his or her death there is a possibility of finding some content of the water in which the drowning took place inside the individual and the region to look for this is the bone marrow. Further diatoms are the phytoplanktons that reach the bone marrow in cases of ante mortem drowning. Diatoms are present in all water bodies, but the species of diatoms present in each water body varies. Therefore, diatoms have been used in drowning cases to prove the person had drowned and the location where the drowning took place. The analysis of diatoms is still in the process of development. Since they have silica-based cell wall they are strong, and their analysis needs to be done in such a way that procedures employed should be accepted by the court as a valid protocol and subsequently admit the evidence in that particular case. Extraction of diatoms from bone samples is an important step to isolate diatoms from the human tissue. There are many ways to conduct this extraction, but the most efficient technique is not known. This study reviews the studies conducted on the acid digestion procedures for extracting diatoms and it is found that acid digestion method can be used for numerous types of samples. Some protocols were tweaked to get the best results but the basic utilization of acids like nitric acid, hydrochloric acid and sulphuric acid showed good results in the extraction of diatoms from samples of forensic significance.