Underwater Crime Scene Investigation
By: Don Penven, Technical Support Group
Most crime scene investigations are conducted using primarily land-based procedures. But the earth’s surface is 70% water, which requires a thorough understanding of underwater investigation techniques for a successful outcome.
While the underwater environment offers significant challenges, the techniques employed still follow the basic crime scene protocols such as protection of the crime scene, interviewing witnesses and victims and maintaining the chain of collected evidence custody.
The single, most important point stressed in much of the available literature emphasizes the need to consider all underwater incidents involving a death be treated as a homicide (until ruled otherwise), and to proceed accordingly in collecting and preserving any possible physical evidence.
Only slight similarities exist in the methods and techniques employed in an underwater search compared with a land-based investigation. The purpose of land and water investigations is to locate and collect evidence that will stand on its own during a courtroom presentation. Either type of investigation is conducted by trained specialists whose purpose is to be certain that nothing in the scene is disturbed until the investigation is complete. Here, any similarity between land and underwater crime scenes ends because the underwater scene requires significantly different equipment, practices and procedures.
Those charged with underwater crime scene investigation (UCSI) must acquire the same basic skills required for any crime scene, but added to this is the need to be thoroughly trained in the proper and safe use of diving equipment. And as is the case with any crime scene, the investigator must possess a high level of skill in underwater photography.
Maintaining crime scene security offers many challenges. The UCSI doesn’t just surround the scene with yellow barrier tape. The investigator must keep in mind that this is not a “salvage operation,” as was often how some underwater scenes were handled in the past.
In today’s world underwater assignments are much more sophisticated, employing specialized equipment coupled with high-tech methods akin to those used in underwater archeology. The precise location of every single artifact at the site is mapped and all evidence recovered is carefully preserved. Thanks to refinements in evidence collection techniques and innovative tools, the evidence can be preserved intact—making it usable for introduction during a criminal trial.
A major problem facing investigators has been estimating the time of death. A body that has spent several days submerged further complicates this finding. Decomposition of a submerged body occurs rather rapidly due to environmental factors such as the presence of marine life, bacteria of many varieties and varying temperatures. These factors combine to confound the investigator at the scene in making it nearly impossible to determine if death was accidental or intentional. It may take weeks or months to arrive at a determination after recovering the body and post mortem examinations are completed.
A factor that influences the determination of a final outcome is the interference of marine life. Crabs and other sea creatures tend to make circular patterns while consuming flesh, which may falsely portray foul play. Marine life can destroy any evidence that may have been left with the body. Most often the body parts consumed first are the eyelids, lips and ears.
According to Gemma Dickson, a forensic biologist from New Zealand, "Unless a body is witnessed entering the water, there is no reliable method for determining the length of time that a body has been submerged”
What has been recently discovered, however, is that bacteria (Phychromonas) first begin to colonize decomposing bodies in the frigid temperatures associated with many free standing, natural bodies of water. It is specific genera in the Bacteroidales order, only colonized after 10 days of submersion, and it can accommodate many different water environments. This bacterium thrives on the fecal matter associated with a decomposing body.
This new discovery could transform the field of general science, forensic and law enforcement studies and how bacteria interact with decomposing bodies. The same researchers in Australia are continuing their research using submerged pig heads and letting them decompose on their own in the water to study these bacteria.
All living creatures, including bacteria, excrete waste into the environment causing noxious odors that are specific to each bacterium. In the case where bacteria are feeding on a corpse, the surrounding soil or water can hold valuable information, so obviously samples must be collected.
Although bacteria prefer an oxygen-enriched environment, they have also been known to survive in anaerobic conditions. Research has found that psychrophilic bacterium was isolated from a cold current off the Monbetsu coast of the Okhotsk Sea in Hokkaido, Japan. The time and seasons of the year seem to have little effect on their growth because of the nourishing environment of the water.
Just as maggots recovered from a rotting corpse can give a good approximation of the time of death, so may microscopic organisms tell the investigator what happened. As in the case with blowfly larvae, maggots, and the pupae stage, growth cycles can give valuable information. Perhaps it will not be long before bacteria will be telling the same story.
The point here is that the scuba-diving investigator should collect soil samples from around and under a submerged corpse, and to collect water samples adjacent from the corpse.
It is also recommended that items collected from underwater be packaged in the water in which it was found. This will reduce the chance of environmental deterioration that may be caused by removing items from the water.
Some basic tools needed by UCSIs will include: magnetometer or underwater metal detector, recovery magnet, hand trowel, sifting screens, underwater lighting equipment, waterproof camera and a variety of evidence containers.
This forensic tool of studying bacterial life cycles can also help aid those interested in identifying the body and giving surviving loved ones closure.
References:
D.P. Lyle, MD: “Time of Death” http://writersforensicsblog.wordpress.com/2010/12/09/bacteria-and-time-of-death-a-new-forensic-tool/ April 4, 2011
Kade, Asher: “Underwater Crime Scene Investigation,” http://www.environmentalgraffiti.com/biology/news-breaking-news-bacteria-tells-time-death-submerged-bodies , April 4, 2011
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