Crime Scene Investigator Network Newsletter

Introduction
Dogs have established themselves prominently in the law enforcement community. In spite of this, cadaver dogs "have been minimally represented in the law enforcement canine population across the United States". Cadaver dogs are also known as human remains detector dogs, forensic search dogs, and decomposition dogs. The term "cadaver" can be misleading because the dog may not always locate an actual body, but may indicate on scavenged parts, body fluids, or the residual odor of a body. For the purpose of this paper, the term "cadaver dog" will mean any dog trained to detect deceased humans, human parts, or residue from human remains.

The odors emitted by a deceased person begin the moment biological death occurs and are not immediately noticeable by humans. The odors are, however, discernable by dogs. Odors associated with dead bodies differ from one individual to the next even though the process of decomposition and the chemical reactions that occur in humans are generally the same. Unlike the drug detector dog which may have to learn only four to six different odors or the explosives detector dog which must learn nine to fourteen different odors, the cadaver dog is exposed to as many as 424 different volatile chemicals producing specific odors. Exactly which odors the dog alerts on during a search is unknown.

Rebmann et al. describe five basic stages and characteristics of human decomposition. During the first stage (the fresh stage), there is little change visible by humans; some dogs may even approach these bodies as though they were alive. However, at this stage, internal decomposition is beginning. In the second stage (the bloated stage), gas is produced within the body, causing it to swell. An odor of decay is present that is detectable by both a human and a dog. Entomological activity may be present at this stage. During the third stage (the decay stage), the gases have escaped the body, exposed skin color changes to a dark or black appearance, and a strong putrefaction odor is present. The fourth stage (the liquefaction stage) occurs as the body begins to dry. The odor produced reduces in intensity, but may become musty. (Galloway classifies this as the skeletonization stage even though body fluids may still be present.) Finally, the last stage (the skeletal stage or extreme decomposition) involves most of the remaining flesh drying to the point of mummification. The musty odor remains but is not as strong, and the distance to which it is detectable is much less than in the prior stages. All of these stages provide many odors that the cadaver dog must be capable of detecting.

Several variables contribute to the decaying process and influence the rate of decomposition. Our bodies contain microorganisms that are essential to life, but also play a role after death. Environmental conditions play an essential role in the rapidity of decomposition as well. The location of the body (e.g., water, swamp, desert, depth of burial) influences the rate of decomposition. According to Bass, rapid decomposition "can only occur under the most favorable conditions of high temperatures and humidity, ample insect infestation, and the body shaded from direct sunlight".

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