Juries love dog testimony. As witnesses go, nothing beats a
canine for sincerity and trustworthiness, and nothing brings a little light into a dismal courtroom like the goofy grin and thumping tail of a hound.
"The jury eats it up," says police K-9 handler Pat McAlhany, a veteran of the Miami-Dade County Sheriff's Office. "From a prosecutor's standpoint, there's nothing better than my actually bringing my dog into the courtroom for a demonstration."
Indeed, the practice of using dogs as "nose witnesses" to finger, as it were, the accused is rapidly growing. A rape case that passed through the Los Angeles court system last year illustrates the procedure. A young woman came into the police department and described a brutal attack. Two men had dragged her from a bus stop in an industrial part of the city into an alleyway, where they sexually assaulted her. Traumatized, she initially did not report the attack. But two days later she found a necklace she thought one of the rapists had ripped from her neck. It lay outside the school where she worked. Did one or both of the attackers live in her neighborhood and know her daily habits? She also spotted a man at a local market who reminded her of one of the attackers. Now terrified, she went to the police.
The delay meant a rape kit could not provide DNA evidence. Not a problem. Enter Reilly, a confident, experienced expert witness with boundless enthusiasm for his job. Under the leash of volunteer scent-evidence K-9 handler Joseph D'Allura, this chocolate Lab's scent-detection skills had put killers behind bars. For the rape case, D'Allura created a "scent lineup," using a scent transfer unit that worked like a Dustbuster, sucking the perpetrator's odor off the snatched jewelry and onto a sterile gauze pad placed over the
vacuum's air intake. He then vacuumed a piece of clothing taken from the neighborhood resident who had aroused the rape victim's suspicions in the local market.
D'Allura prepared the scent lineup by placing the suspect's pad alongside three decoys infused with scent from other individuals. Finally, he presented Reilly with the necklace scent pad and directed him to find its match. Passing over pad number one, the dog gave the second sample a wag and a bark—
an "alert" in dog-handling lingo. The police had a positive ID.
Or did they? Juries may love a dog show, but some experts remain skeptical. "In all honesty, we don't know what a dog is picking up on when it alerts," says Lawrence Myers, an Auburn University sensory and behavioral biologist called as an expert witness for the defense in the rape case. Over the past 21 years Myers has trained more than 50, and studied hundreds, of scent-detecting dogs under laboratory and field conditions, mostly for federal agencies wanting to perfect the use of dogs for finding explosives, drugs, trapped disaster victims and hidden graves.
Myers considers the canine nose the ultimate odor-detection system in use today. But in many ways, he says, "we're still dealing with a black box." Scientists have yet to fully understand the process of canine odor identification. Neither have they defined the limits of a dog's sense of smell, nor isolated any universal "scent factor" that dogs use to distinguish one person from another.
The widely held view is that dogs pick up on variations in the chemical makeup of the skin flakes and perspiration residue we all continually shed. But no one knows which aspects of this microscopic brew grab a dog's attention as it plays a forensic game of mix and match. Might racial or gender differences skew results? Or, for that matter, some yummy-smelling food the person ate the previous day?