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Growin' Our Own (page 4)

With dog detectives, mistakes can happen

By: Mark Derr

When bomb-sniffing dogs indicated the presence of explosives last summer in the cars of three medical students bound for Miami, the authorities detained the men and closed a major thoroughfare across South Florida. No trace of explosives was found in their cars.

Now, a number of scientists and trainers are expressing concern that such mistakes could become more common as thousands of new canine detectives are deployed across the country. Experts on explosives detection say that when dogs' handlers are excited and stressed, the dogs may overreact and falsely suggest that explosives are present when they are not. False alerts are better than missing a live bomb, they say, but it is better for the dogs to be accurate.

More rigorous training and certification standards and more research into the way dogs detect scents and the relationship between them and their handlers are needed to avoid these problems, said Dr. Lawrence J. Myers, an expert on dog olfaction at the Auburn University College of Veterinary Medicine.

Dogs are far better at sniffing out the source of a particular odor than any machine yet developed, experts say. They are also more manageable and culturally acceptable than rats and other animals adept at detecting scents.

Scientists have estimated that a dog's nose has about 220 million mucus-coated olfactory receptors, roughly 40 times as many as humans.

When a dog sniffs, chemical vapors - and, perhaps, tiny particles - lodge in the mucus and dissolve, sending electrical signals along the olfactory nerve and ultimately to nearly all parts of the brain. In dogs, the vomeronasal organ in the roof of the mouth and two branches of the trigeminal nerve in the nasal cavity also play roles in scent detection.

Skilled trainers have taught dogs to detect just about anything that emits even the faintest odor, including explosives, underground oil and water leaks, contraband food, termites, guns, drugs and cash. But in most cases, scientists have not measured the lowest levels of odor that dogs can detect.

Training and handling dogs is an art at which some people excel, and together top dogs and top handlers can perform extraordinary feats. But there are limits on dogs' performance that are frequently overlooked. Poor handlers alone, Dr. Myers said, can cause dogs' vaunted accuracy rate of 85 percent to 95 percent to plummet to 60 percent, Dr. Myers said.

"Dogs want rewards," he added, "and so they will give false alerts to get them. Dogs lie. We know they do."

Determining how accurately dogs in general detect particular odors is difficult, experts say, because procedures vary from place to place, and few have been subjected to rigorous scientific testing. Though some dogs and handlers are consistently good, all may vary in their daily performance.

When dogs are asked to identify people, the situation is even more complex. This use of dogs is based on assumptions that every person has a unique scent, that odor is stable over time and that dogs can tell one person from another. But the first two assumptions have not been fully verified and the last is not always true, said Dr. Adee Schoon, scientific adviser to the Netherlands National Police Agency Canine Department.

"You need special handlers and special dogs for identifying suspects," said Dr. Schoon, who recently visited Florida International University in Miami to present a seminar on scent identification at its International Forensic Research Institute and to discuss collaborative research.

In the 1990's, Dr. Schoon documented that the Dutch procedure for identifying suspects with dogs was prone to substantial errors. Then, she redesigned it.

Her biggest achievement, she said, has been discrediting people who say, 'My dog never errs.' Scent identification in Holland is now conducted under controlled circumstances to minimize human and dog errors. Investigators ask the suspect and six "foils," who have had no involvement in the crime, to hold small steel tubes briefly.

The tubes are then lined up on a platform in parallel rows of seven each in a pattern unknown to the handler. The dog's task is then to match a scent from the crime scene to tubes in two rows.

The dog performs two tests, the first to prove that its nose is on target and that it has no interest in the scent of the suspect, by tracking down the tubes touched by a foil.

In the second, it identifies the suspect, if that person's scent is present, from scents taken at a crime scene. The dog works off its leash to minimize the handler's influence. "All kinds of problems" arise when a dog is asked to match scent to an actual person, Dr. Schoon said. For one thing, she said, the handler may unconsciously direct the dog toward a particular suspect.

Dogs are also known to become fixated on people for no apparent reason and to return to them again and again, Dr. Schoon said. Without the first test run in which the dog is asked to find another "suspect" in the same group, it is very difficult to tell when a dog is becoming fixated for no apparent reason, she added.

Dr. Steven J. Hatfill, a bioweapons expert, was identified by federal law enforcement authorities this summer as "a person of interest" in the anthrax inquiry based in part on scent-matching by three bloodhounds.

Pat Clawson, a spokesman for Dr. Hatfill, questioned the circumstances surrounding the use of bloodhounds and said the dogs' responses were inadequate to link Dr. Hatfill to the anthrax letters. No charges have been brought in the case.

Experts say other problems can emerge when the dog is faced with only one person. Because dogs are regularly rewarded for choosing suspects in training, they are predisposed to say yes when asked to match scents in situations involving only one potential suspect, experts say. It takes time to train an animal to say no in such cases.

Edward Hamm, a member of the Southern California Bloodhound Handlers Coalition and one of the bloodhound handlers involved in the Federal Bureau of Investigation's anthrax work, said that all three dogs in the Hatfill case were specifically trained to say no, but he would not discuss any details of the case. Paul Bresson, an F.B.I spokesman, also declined to comment.

Determining the accuracy of detection and scent identification dogs is often difficult. Certification standards for dogs and handlers vary markedly from state to state and agency to agency. Written training logs, which are used to establish a dog's reliability in court, are themselves often unreliable.

"There is a saying in Holland that the training log is a lie," Dr. Schoon said, if only because handlers want their dogs to look good. It is not known how often this problem crops up in the United States. Dr. Myers said: "The standard measure of a dog's accuracy is what it finds. The best programs subtract from that score the number of false alerts, but most do not and so they have no accurate measure of their dogs' reliability." He is helping to create software to assist handlers and trainers in selecting, training and maintaining their dogs at optimal levels.

Maine Specialty Dogs in Alfred trains dogs for fire departments around the country to search burned out buildings, often for minute traces of flammable compounds that may have been used in arson, said the head trainer there, Paul Gallagher. Sponsored by State Farm Insurance, the school selects, trains, certifies and recertifies about 100 "arson dogs" a year. No dog that has even one false alert in its final proficiency test receives certification, he added.

Around the country, a few other programs are equally demanding. Secret Service bomb dogs, considered among the best in the world, are retested weekly and must have an accuracy percentage in the upper 90's, said a spokesman, Brian Marr.

While concerned about missed targets, many trainers and handlers deny that their dogs sound false alarms, and so they do not record them, especially if they occur in the field. They argue instead that the dog is picking up a faint trace of a substance that was once present, or that a handler caused the dog to err.

Handlers can create errors by pulling their dogs away from things they are investigating, by letting them search too long in a single place or by inciting the dog through some gesture, glance or emotion, even unconscious. Trainers say the message "travels right down the leash."

Mainly for that reason, the few studies of dog performance that have been done suggest that dogs perform best off their leashes.

Off-leash work is common in Europe, but for a variety of social and legal reasons, dogs are worked almost exclusively on-leash in the United States, said Dr. Paul Waggoner, interim director of the Canine and Detection Research Institute at Auburn.

Other factors can also hurt a dog's performance, Dr. Myers said. He estimates that in any year, 35 percent of detection dogs temporarily lose their sense of smell because of illness, tooth decay or other physical problems.

Weather also affects performance. Dry, hot weather can cause the mucus in the dog's nose to dry out. Hot, humid weather brings early fatigue. Extreme cold kills scents, and the wind scatters them. Creatures of habit, dogs also can become stuck in their ways. For example, a dog might become fixated on a particular object or smell, Dr. Myers said, citing a police dog in Alabama that began alerting its handlers to Ziploc bags because the police stored drug training samples in them.

In the 1990's, researchers at Tel Aviv University showed that dogs would begin to slack off if they were given fewer samples to sniff for than they had been trained to find.

The researchers also found that after several days of patrolling an area, like a stretch of road, the dogs would give up if they discovered no explosives.

As a result, bomb-sniffing dogs in Israel are continually rotated to new areas on patrol, said Dr. Joseph Terkel, the professor of zoology at Tel Aviv University who directed the research, conducted by a doctoral student, Irit Gazit. Trainers also vary the number, size and concentration of targets, down to zero, in practice and include "blanks" with different scents, which the dog should ignore. Because Israeli bomb dogs work off-leash, 50 to 100 yards ahead of their handlers and often out of sight, the Tel Aviv researchers several years ago developed a miniature microphone that fits on the dog's nose and allows the handler to hear whether the dog is panting or sniffing.

A panting dog cannot sniff. A radio receiver allows the handler to recall the dog and send it out to search a specific site again if necessary.

The practice of training dogs on substances concocted to replicate the primary odors found in drugs or explosives can also lead to error, said Dr. Kenneth G. Furton, director of the forensic science program at Florida International University.

Studies have shown that different dogs respond to different components of an odor and that those components change over time. So dogs accustomed to a concoction used in training may have a hard time recognizing the more complex bouquet of the actual substance.

Experts say more research may resolve uncertainties and maximize dogs' performance. Meanwhile, they say, training and certification standards should be tightened to ensure that dogs and handlers are as reliable as possible.

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