If you want to find a corpse, Fido might be your best choice. While there are plenty of other methods that law enforcement officers use to try and track down dead bodies, like systematic searchs along transects and ground penetrating radar, specially-trained dogs are still the most reliable of the three.
The smell a person gives off after they die is unique to humans and is incredibly complex, which dogs can be trained to detect. In fact, humans release 478 different chemical compounds as their bodies decompose. And researchers still don’t know which ones in particular stand out to Human Remains Detection (HRD) dogs, writes Kiona Smith-Strickland for Gizmodo:
Whatever the chemical signature is, it’s present through the whole process, from fresh corpses in the first few hours after death to skeletons several years old. It’s also present in several types of tissue, including blood, bone, and fat. Properly trained HRD dogs can identify the scent not just in whole bodies, but in blood spatter, bone, and even cremated remains. They can even pick up the scent left behind in the soil after a body has been removed from a grave.
HRD dogs can even tell the difference between the smell of a living and dead person. But even the dogs need a lot of training to be reliable death-detectors. While some have experimented with synthesizing some of the chemicals produced by decomposing corpses, such as the aptly-named cadaverine and putrescine, a 2004 study didn’t find any noticeable traces of either chemical in or around gravesites.
“In order to learn to find something by scent, dogs need to practice with the real scent,” Smith-Strickland writes. “That’s why, for example, handlers who train drug dogs are allowed to work with actual narcotics for training. So, to learn how to find dead people, HRD dogs need to practice on – you guessed it: actual dead people, or body parts.”
Human remains aren’t the easiest thing to come across (legitimately, that is), which makes it both hard to train HRD dogs and difficult for scientists to study the scent of death. While there is some evidence the smell may emanate from bones, researchers have yet to come up with a definitive answer. In the meantime, a gruesome game of fetch is still the best way to find human remains.