Police and search and rescue units are sometimes assisted by service dogs—animals that are specifically trained to search out the source of very specific smells like explosives, drugs, paper money, firearms, or people. Cadaver dogs are specially trained to identify the smell of decomposition, and they can be paramount in determining the location of missing human remains, even when those remains are scattered by scavengers.
When a body decomposes, a host of very aromatic sulfur- and nitrogen-based organic compounds are produced. While they may smell putrid to a human in close quarters, the human nose is simply not sensitive enough to detect this smell at great distances or if the body is buried or covered by running water. A dog’s nose is, on average, 1,000 times more sensitive than a human’s, and some breeds are even more so. Some of the more popular breeds used in police or search and rescue units due to their extra-sensitive noses are German Shepherds, basset hounds, blood hounds, beagles, Labrador retrievers, and spaniels.
Dogs and their handlers are trained using decomposing animal sources, autopsy samples, and desiccated human bones, as well as simulated decomposition compounds. One of the challenges of cadaver dog training is training detection across the spectrum of decay scents from putrefaction to skeletonization so the animal can identify a body at any stage postmortem.
The animals are trained to be both trailing and air scent dogs. Trailing scents are useful if a body has been moved and bodily fluids have fallen to the ground; the dog will follow the scent along the ground until it can find the source of the trail. Air scent dogs will follow an odor in the breeze that is blown outwards in a widening cone shape from the source. The smell will become stronger the closer the dog comes to the source, and the dog is trained to follow that more concentrated scent.
When a cadaver dog locates the source of the compound it is trained to recognize, it will ‘alert’. The alert is specific to each animal or trainer and is instantly recognizable to that trainer—a bark, or the animal sitting or lying down to indicate recognition of the smell in that particular location.
With the help of handlers and fully trained cadaver dogs, human remains can be found following clandestine burials, natural disasters or missing persons searches. Once the remains are found, then the process of identification and determining the cause of death can begin, allowing closure for the family, and, perhaps, justice for the dead.
Photo credit: Canadian Search Dog Association