Drowning is one of the most difficult causes of death for the medical examiner to determine. You would think he would simply have to find the lungs filled with water to make this call but that’s not the case. If a corpse is tossed into a body of water, the lungs will passively fill with water as the air escapes and is replaced with the liquid. So the simple finding of water-filled lungs does not prove the cause of death was drowning.
But the medical examiner has a couple of tricks that can sometimes help. Though not always present, if he finds debris within the mouth and lungs as well as damage to the nasopharynx and the airways, both of which result from the victim struggling for air but only breathing in water, these findings would suggest that the victim was alive when he entered the water. Debris deep within the lungs can’t get there passively and must be inhaled.
And in some cases, diatoms can help.
Diatoms are microscopic organisms that live in all types of water. They can be found in oceans, lakes, and your own bathtub or swimming pool. These tiny creatures are protected by a silicon–containing shell that is quite resistant to damage. They survive in a corpse for a long time. Though controversial, they can be used for determining if someone drowned. In this circumstance, as water is inhaled in the lungs, these diatoms worked their way from the air sacs of the lungs into the bloodstream and from there escape into the tissues, particularly the bone marrow. The medical examiner can test the bone marrow of a suspected drowning victim and if he sees a large number of diatoms then he might conclude that the victim died of drowning.
Now it seems that diatoms might also help locate where a crime took place in cases where the corpse has been moved and the victim’s clothing contacted water. A recent study in the journal Forensic Science International suggests that diatoms can be found in the victim’s clothing. Cotton clothing that has contacted water will absorb and retain the diatoms from that water. If these can be located and identified then they can often be traced back to the source. Diatoms vary from location to location so comparing those found on the victim’s clothing with those of a certain location might be useful in placing the body at that location.
This can be very useful to investigators when a person has been killed near a body of water and then their corpse is dumped at another location. Locating the primary crime scene–the place where the murder took place–is extremely important to investigators since this often results in finding further evidence that leads to the perpetrator. If these diatoms can help make that connection, they might prove to be a useful investigative tool.