Canine investigators taking a bite out of crime

Picture it: Eight men of assorted shapes and sizes standing in a typical police lineup. But in this scenario there is no nervous witness or victim watching from behind a one-way glass, hoping to identify a face and link it to a crime.

Instead, the door opens and in bounds a large Alsatian. The dog runs in between the men, sniffing. Within minutes, he sits down in front of one of the suspects, his tail wagging as he barks his confirmation.

Once the dog has pinpointed the perpetrator, thanks to his amazing olfactory capabilities, law enforcement officers take over and the CSI (canine scene investigator), gets a tasty reward for a job well done.

The nose knows
While they don't yet have their own network TV show, canines are increasingly becoming recognized crime technicians. There’s no doubt about it — the nose knows. And “scent-line-ups” are becoming more common as these highly trained dogs play a growing role in crime investigations.

Like most dogs, canine scene investigators are capable of making a fine distinction between scents. They can get a “scent picture” of one scent even when other scents are present. It’s been said that when a dog walks into a bakery, he doesn’t smell cake, but the flour, eggs and butter.

“Dogs are great detection tools,” says Liz Burne, a canine trainer, who, together with her springer spaniel Lionel, a search-and-rescue dog, has worked many successful cases with the Connecticut Canine Search and Rescue team.

Search-and-rescue dogs are divided into two kinds: air-scenting dogs and trailing dogs. Air-scenting dogs are trained to find any human scent, explains Burne. "Consequently they can locate and alert their handler to any human in the search area."

Humans are natural scent generators — they emit odors through respiration, perspiration and the shedding of skin cells and hairs. Air-scenting dogs work off-leash and can trace a human scent without the aid of an article that was worn or handled by the subject of the search.

The advantage to air-scenting dogs is that there is no need to keep the search area clear of other searchers. If there are other searchers in the area, the dog will find them, be rewarded and sent out again until they locate the intended scent source, which is the person alive, dead, or even under water.

Hot on the trail
In contrast, trailing dogs are "scent specific" and will follow the path the subject traveled rather than trace a scent to its strongest point, explains Burne. They start off with a scented article, typically an item of clothing recently worn by the subject, and track the scent to the subject's location.

To assist them in their work, human crime scene investigators often use a “scene sleeve," a special receptacle that captures and contains the odor. This allows the scent to be transported, usable for multiple dogs and preserved for future use, such as scent lineups.

Despite their amazing olfactory skills, there are limits to dogs' usefulness at crime scenes. “While dogs can be sent into the field wearing a GPS tracking device, I can't ever envisage Lionel in little latex booties marking things with flagging tape,” says Burne. “Dogs are trained to give a passive alert, typically sitting or laying down next to the evidence. This keeps them safe. It would be dangerous having them retrieving evidence, like a gun, and disturbing crime scenes.”

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