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| Théodore Géricault - Le Radeau de la Méduse (1819) |
Not even 12 feet of soil
can get between these dogs and a corpse.
Cadaver dogs search and
rescue golden retriever
By Lucy Huang on July 27,
2017
In mid-July, a
frustrating search for four missing men in Bucks County, Pennsylvania
ended with the discovery of Dean Finocchiaro’s corpse buried in a
suburban farm. The grisly unearthing led the killer, Cosmo Dinard, to
confess to the murders of all four men. Though solving the crime
required about 50 law enforcement investigators and the FBI, the it
couldn’t have been done without the cadaver dogs. They managed to
sniff out Finocchiaro’s body, even though it was buried 12 and a
half feet (presque 4 mètres) underground. These dogs have their
work cut out for them. Unlike drug- or bomb-sniffing dogs that just
need to identify a few specific scents, cadaver dogs must learn to
identify hundreds.
Training requires a lot
of exposure to a lot of putrid odors, but acquiring isolated versions
of those odors isn’t easy. That’s why there’s a macabre realm
of science research focusing on identifying the smells that leach out
of the dead — and isolating them for dogs (and their humans) to
identify. Cadaver dogs usually
start their training between the ages of 18 months and 2 years.
When cadaver pups first
start out, they practice not with real corpses but with synthetic
cadaver scents. These are a real thing: the chemical giant
Sigma-Aldrich makes three different corpse scents for canine
training, including “recently dead,” “decomposed,” and
“drowned victim.” But when it comes to the scent of dead bodies,
nothing beats the real, multifarious stench.
Human bodies decompose in
five basic stages, and each of those stages produces dozens of
different odors. In an attempt to classify them, researchers from Oak
Ridge National Laboratory and the University of Tennessee teamed up
with the FBI to build a “decompositional odor analysis database.”
In a 2004 article in the Journal of Forensic Science, they explained
their process: First, they buried four bodies in graves between 1.5
and 3.5 feet deep and, over the course of the next year and a half,
used traps to capture the air that emanated from the rotting bodies
through the ground. After analyzing 374 samples from the graves, they
found out just how many volatile chemicals the human body makes when
it decomposes: a whopping 424.
Many of these scents are
likely identifiable only by trained dogs, but a few will stick out
even to the common human nose: cadaverine, putrescine, skatole, and
indole. These compounds smell
particularly rank:
Cadaverine, the smell
of which is officially classified as “unpleasant,” is responsible
for the foul smell of rotting flesh and is also found in urine and
semen. Putrescine, which smells fairly similar to cadaverine, is also
what makes bad breath bad. Skatole — which is also found in coal
tar — and indole are major components of feces. Strangely enough,
skatole and indole are also used in low concentrations to develop
flowery scents for perfumes. Complicating the smell of
death is the fact that the environment in which a corpse decays
affects what odors are produced. In 2016, researchers from the
University of Leicester reported that soft tissue that decomposes in
the absence of oxygen breaks down differently than soft tissue in the
presence of oxygen; in other words, corpses in the ground and above
ground rot differently. Studying gas samples taken from pig hearts,
the researchers found that decomposition in oxygen-free settings
produces a lot more of indole, while the presence of oxygen tends to
lead to high levels of acetone.
Of course, when it comes
to training cadaver dogs, nothing beats the real, gruesome thing.
Trainers can bring dogs to outdoor forensic decomposition
laboratories, like Western Carolina University or the Penn Vet
Working Dog Center to practice finding actual dead bodies. As with
all dog training, sniffing out cadavers comes down to manipulating
the dogs’ “response and reward systems” through positive
reinforcement. Despite the fact that a
dog’s sense of smell is 100 to 1,000 times more sensitive than a
human's, these dogs still need to put in a lot of practice — the
training process usually spans from 18 months to two years. But all
that time and dogged sniffing pays off: When it comes to finding a
corpse buried deep underground — even if it’s “hundreds of
years old,” according to cadaver dog expert Cat Warren — these
death-sniffing pups are still more effective than any machine.
