Daily Archives: October 13, 2009

Electronic Noses: Sniffing Out Corpses

When someone is reported missing and it is assumed that they’ve been murdered and dumped somewhere, it is critical for the police to locate the body, since this often gives them the critical clues that they need to determine who the killer was. There may be biological evidence associated with the body such as saliva or semen or blood or skin tissue under the victim’s fingernails. There might be hair or clothing fibers from the attacker. He might have left a fingerprint on the victim’s purse or belt or windbreaker or some other surface that would accept and hold prints.

Finding the body is critical.

The current Drew Peterson case comes to mind. The fact that his most recent wife disappeared and her body has yet to be found is greatly complicating the police investigation into her disappearance. And what about the other Peterson–Scott? Had the bodies of Laci and the unborn Conner not risen from the watery grave Scott gave them, he just might have gotten away with murder. Finding the bodies brought closure to the later Peterson case and hopefully will someday do the same for the former.

How are bodies located?

Let’s say that a young woman walks or jogs through a park or a wooded area on a regular basis and one day disappears while on one of these walks. The police would search that entire area, assuming that if the attack took place on that trail, the body would likely be left somewhere near that path.

First the police would spread out along the trail to see if the body was left nearby. If this was a murder of passion or of opportunity, the killer might not have a plan for body transport and disposal so he would want to get rid of the corpse as quickly as possible. That means he likely dumped or buried the corpse near where the attack took place. So, the best place to look would be near the trail—particularly on the downhill side. Dead bodies seem to weigh a lot more than the person did when they were alive (not true just seems that way) and carrying a dead body uphill is not easy. Downhill works much better.

Investigators would look for disturbances in the ground or interruptions in the normal vegetation that might reveal a recently dug grave. Freshly turned dirt, trenches, or elevations or depressions in the terrain might be helpful. Fresh graves tend to be elevated above the surrounding area, while older ones might be depressed. This is due to settling of the soil, decay of the body, and collapse of the skeleton. Interestingly, the depth of the depression is greater if the body is deeply buried. This is likely due to the larger amount of “turned” dirt, which is subject to a greater degree of settling and the increased weight of the dirt over the corpse, causing earlier and more complete skeletal collapse. This leads to a deeper depression in the soil.

If the corpse has been buried for a number of weeks or months, changes in the natural flora of the area might be seen. Decomposing bodies tend to make good fertilizer and often the flowers and shrubs that grow near the burial site will be fuller and more lush than those in surrounding areas. Often aerial reconnaissance from a plane or helicopter can uncover this. In addition, the plane could be equipped with infrared and other thermal devices that look for heat signals. Freshly turned dirt tends to lose heat more rapidly than does compacted soil so that thermal scanning might turn up a “cold spot.” On the other hand, an actively decomposing body tends to produce heat as one of the byproducts of decomposition and this might be visible on an infrared scanner as a “hot spot.” So any variation from the background level of heat found by thermal scanning should be investigated by searchers on the ground.

Other scanning devices are also used. Ground penetrating radar and side scanning sonar can often be used to locate bodies. In a fairly fresh grave, the soil is looser, less compacted. In addition, a decomposing body tends to add moisture to the soil. These types of scanners can often detect this loosened and/or more moist soil and thus locate the grave. Also, a simple metal detector might locate jewelry, belt buckles, cell phones, watches, or other metallic objects that the victim had on her at the time of burial.

A magnetometer is a device that looks at the magnetic properties of soil. In many areas, the soil contains small amounts of iron, which gives it a low level of magnetic reaction. Since the body itself has a lower magnetic reactivity than the soil, the magnetometer can sometimes detect this variation and help locate buried corpses.

Dogs play an important in corpse location.

Bloodhounds or other tracking dogs might be useful in that they can often track the victim from her home, along the trail, and then to the dump or burial site. Some bloodhounds have even tracked corpses that were transported short distances in automobiles.

Cadaver dogs might be brought in. These dogs are specially trained to sniff out the chemicals of decomposition. When a body decays it releases certain chemicals and these dogs are trained to locate them. They can find a body that is only a day or two old and in some cases ones that have been buried for 20 years. The reason is that the gaseous molecules that are produced during the decay process tend to hang around in the soil for a long time and are slowly released into the air. Though humans might not be able to detect the odor, a well-trained cadaver dog can.

But the days of these detective dogs just might be numbered.

More recently scientists have begun developing what is known as an Artificial Nose, Electronic Nose, or E-Nose. This is simply a device that detects the chemicals of decomposition as they are released into the air around a dump or burial site. It works on the same basis that a cadaver dog does. The released chemical molecules strike specialized receptors within the dog’s nose and if he is trained to recognize these chemicals he will alert his handler to that fact. The electronic nose has sensors that detect the same chemicals.

Many of these devices are simply small portable gas chromatographs, which can separate and identify many chemicals and in some cases determine the amounts of each. Newer studies are looking into using the new technology of microfluidics and LOCAD— Lab On A Chip. These are a spinoff of current research going on at NASA’s Marshall Space Flight Center in Alabama and other areas around the country.

Other uses of such an Electronic Nose would be to detect harmful environmental chemical contaminants, screen for bioterrorism toxins, and maybe even complement fingerprints and DNA as a method for identification. Sort of an Odor Print.

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