Crime Library: Criminal Minds and Methods

K-9 Forensics

The Scent Pad

In 1977 in Cheektowaga, New York, a police officer was shot and killed at a Holiday Inn. An article containing the fugitive killer's odor was found, and 11 different law enforcement agencies responded with German shepherds and trailing bloodhounds to join the ensuing manhunt. However, the first dog had contaminated the article, which rendered it useless. William Tolhurst, a member of the Niagara County Sheriff's Department and an authority on man trailing bloodhounds, was among those who showed up to help. The incident inspired him to develop a way to preserve the scent and keep it away from contact with the dogs.

A scent sleeve (Bill Tolhurst Enterprises)
A scent sleeve
(Bill Tolhurst Enterprises)

Thus, he invented the "scent sleeve" in which scented material could be placed for protection. This device operated by pumping air over the scented article to push the scent into a receptacle. The receptacle captured and contained the odor, making the scent not only usable for multiple dogs but also quite portable.

The Big T Trainer <br />(Bill Tolhurst Enterprises)
The Big T Trainer (Bill Tolhurst Enterprises)

A decade later, Tolhurst developed the Big T Trainer, where a scented item was placed in a container through which pressured air blew to deliver the scent wherever he needed it. Any kind of scent, from accelerant to cadaver, could be used. That, too, proved effective, but Tolhurst didn't stop there. He then developed a vacuum process to collect the scent into a sterile gauze pad, which could be stored indefinitely and transported to different locations. Finally he made the device itself portable, calling it the STU100 (Scent Transfer Unit).

With this invention, scent can be picked up even from arson and explosives scenes, and can be freeze-dried for long periods of time. That means the pads can be used several years later in the event they're needed in a court case. Scent can also be removed from water, metal fragments, and fingerprints, leaving everything at the crime scene intact. Even more surprising, it can be collected from the air in a building where someone broke in. The key is to give it to the dog and let the dog follow it or pick out the suspect in what's come to be known as "scent line-ups."

In one case, as reported by Bill Clede, Tolhurst was on an arson team that was trying to crack a series of crimes in which fires had been deliberately set around Niagara County. When they found a suspect, they surreptitiously acquired an article with his scent on it. Tolhurst made a scent pad, and with this he eventually linked three of the fires to the suspect. The officers confronted the man and he confessed.

Tolhurst calls scent "the forgotten evidence," because investigators just don't think about it. It's delicate, can't be detected well by humans, and isn't visible. However, it can be powerful and in some cases, it might be the only available evidence. There is always a scent.

Perhaps one of the more demanding jobs of a dog handler is that of a human remains specialist. The next chapter features an interview with one of these trainers.


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