Three keen-nosed bloodhounds named Lucy, Knight and TinkerBelle, flown in by the FBI from Southern California late last summer to help with the anthrax investigation, are a major reason for agents' focus on former Army bioterrorism expert Dr. Steven J. Hatfill, according to sources with knowledge of the case.

But the three bloodhound handlers brought into the anthrax case - who also helped with the Washington-area sniper investigation - use equipment and techniques that are rejected by many others in the field, including both of the major police bloodhound associations.

It is uncertain what, if any, other evidence the FBI may have against Hatfill, a 49-year- old physician and biologist who worked at the Army's biodefense center at Fort Detrick from 1997 to 1999. Hatfill adamantly denies having anything to do with the anthrax attacks, saying he has been targeted by investigators desperate to show progress in the year-old case.

News media reports and scientists' views on the likely source of the mailed anthrax that killed five people last year remain strikingly divided. Last week, ABC News reported that the bloodhounds were the FBI's "secret weapon" in firmly linking Hatfill to the anthrax letters. Yesterday, The Washington Post published a report suggesting that the anthrax in the letters might actually have been produced by a bioweapons program in Iraq or some other country, not by a renegade U.S. scientist as the FBI appears to believe.

FBI spokesman Paul Bresson said yesterday that investigators have ruled out no possible source. "We're exploring all leads and letting the facts take us where they will," he said.

Whatever the FBI's ultimate conclusion, the controversy over the bureau's use of bloodhounds reveals a surprisingly haphazard approach to enlisting outside forensic help in one of the largest investigations in U.S. history. If charges are ultimately brought against anyone, the debate over how the dogs were used could be a hurdle in proving the case.

Unlike even many midsize police departments, the bureau does not have its own bloodhounds or handlers so it must recruit outsiders.

In this crucial case, the 15-year FBI veteran who selected the handlers and dogs is an explosives expert who says he has no experience using bloodhounds himself. Agent Rex Stockham acknowledges that the California handlers and their methods are viewed skeptically in the field, though he says the critics base their opinions on prejudice, not evidence.

"The guys in Southern California are social outcasts in the bloodhound handling community," said Stockham, a forensic examiner in the explosives unit at the FBI Laboratory in Washington.

'Talking trash about us'

The two major associations, the Law Enforcement Bloodhound Association and the National Police Bloodhound Association, "are out there talking trash about us," Stockham said. In fact, he said, he was virtually "laughed out" of one training seminar at which he tried to present results of the California handlers' work.

Jerry Nichols, a Colorado police officer and president of the Law Enforcement Bloodhound Association, does not mince words in criticizing the Californians.

"These are people we have credibility problems with," said Nichols, who has worked with bloodhounds for 13 years, conducted more than 500 bloodhound searches and testified in court 21 times. "I'm extremely skeptical. I don't believe these dogs really do what they claim to do."

A half-dozen other handlers interviewed by The Sun expressed similar doubts, including veteran Maryland police bloodhound handlers who admitted being irritated that the FBI had flown dogs across the country for searches that were mostly in the Frederick area.

But the critics have not dissuaded Stockham and the FBI from using the three handlers and their hounds - Bill Kift, a police officer in Long Beach, Calif., and his dog, Lucy; Dennis Slavin, an urban planner and reserve officer with the South Pasadena Police Department, and TinkerBelle; and Ted Hamm, a civilian who runs his own bloodhound business and is used by the Los Angeles County Sheriff's Department, and Knight.

"It's new," Stockham said of techniques used by the three men. "It's going to be criticized. I'm critical of it myself. I'm evaluating it for the FBI lab."

Stockham said he first became acquainted with the three handlers after seeing a 1999 video of their experiments with taking scents from fragments of exploded bombs.

But Stockham said he could not comment on the use of the bloodhounds on the anthrax case, the sniper case or any other open case. He also said the FBI had asked Kift, Slavin and Hamm not to comment; they did not return phone calls.

Truc Do, a Los Angeles County deputy district attorney who has prosecuted cases successfully based in part on blood-

hound evidence produced by Slavin and Hamm, said the critics are misinformed. She said the California handlers are very careful to test their techniques before trying them on real cases.

"They've been working at the forefront of this kind of evidence," said Do. She was skeptical at first but has been won over: "You really have to see it to believe it."

Traditionally, a bloodhound handler uses a "scent article" to start his dog looking for a trail left by the person who had contact with the article. For example, a dog might be given an item of a missing child's clothing.

Then, on command, the dog sniffs around an area for a matching scent. If the dog picks up the child's scent, it trails with nose to the ground until it finds the child or the point where, for instance, the child was pulled into a car.

Instead of using the original scent article, handlers often put a small gauze pad on the item - clothing, facial tissue, a steering wheel - and allow the gauze to absorb the scent before preserving the "scent pad" in a plastic bag.

Pushing the limits

But the Californians have pushed the limits of the bloodhound art, taking scent off shell casings from firearms used in crimes, fragments of exploded bombs - and the decontaminated anthrax letters.

The Californians often use a $895 machine called a Scent Transfer Unit, resembling a small vacuum cleaner, that is designed to draw the scent off the article and deposit it on the pad. One of the machine's inventors is Larry R. Harris, a veteran bloodhound handler who trains with Slavin, Kift and Hamm.

Neither of the two police bloodhound associations has endorsed the Scent Transfer Unit. Officers of the two groups say it offers little advantage over using a gauze pad alone and in fact might confound matters. They contend that an older scent might linger in the machine when it is used on a new case - a charge its users deny.

In addition, bloodhound experts say, the Californians have been quite aggressive in using the dogs not only to follow fugitives or missing persons, but also to identify potential suspects - such as Hatfill - out of a number of people who might have committed the crime.

A false positive

That raises the possibility of a false positive - the identification of an innocent person as the perpetrator, with dire consequences. Some handlers say that there is always a chance that an eager-to-please dog will identify someone even if there is no scent match.

I. Lehr Brisbin Jr., a University of Georgia biologist who has a doctorate in animal behavior, is one of the few scientists who has actually tried to test dog handlers' claims that a bloodhound can accurately pick out a perpetrator from several suspects. He has conducted numerous experiments in which the bloodhound tried to pick from a half-dozen people the one whose scent was on a baseball cap, he said.

No dog was able to do it consistently.

"As a scientist, what they're supposed to have done [in the anthrax case] sounds like a miracle," said Brisbin, a bloodhound handler himself. "Every time I ask a dog to identify a suspect under controlled conditions, the dog can't do it."

Indeed, a federal jury awarded $1.7 million last year to a man wrongly accused of rape after police identified him in part based on the use of Slavin's bloodhound, TinkerBelle. DNA evidence later proved the man, Jeffrey Allen Grant, had not committed the rape.

Hatfill's attorney, Victor M. Glasberg, has suggested that such a mistake might have occurred with the bloodhounds used in the anthrax case, which he has ridiculed as "bionic dogs."

While few details of what the California handlers did in the anthrax case are known, Hatfill said through a spokesman that a bloodhound entered a room where he was sitting and approached him, prompting one agent to call out that the dog was identifying him.

Similarly, William C. Patrick III, another bioterrorism expert, said he and his wife were asked to stand on their lawn in Frederick, and two bloodhounds were led near them.

"They released the dogs, maybe 10 feet away," Patrick said. "My wife and I are dog lovers and we called them, and they walked up and we patted them." Patrick said he was told the dogs had not identified him as the perpetrator.

'Too many variables'

Cpl. Douglas H. Lowry, the senior bloodhound handler for the Maryland State Police, said that if he had been asked to take his dog to potential suspects' houses or approach suspects to see whether the scent from the letters could be matched, he would have refused to try.

"I think there's too many variables," said Lowry, a handler for 23 years who works from the Hagerstown barracks. "Let's say there's a cat or dog that urinated on the floor. You're going to have to be a pretty good handler to tell [the dog's reaction to] that from identifying the suspect."

In addition, Lowry and several other bloodhound handlers say they are doubtful that a useful scent could be taken from the anthrax letters. They note that the perpetrator probably minimized handling of the letters because no fingerprints or DNA could be recovered from them.

Then the letters went through the postal system, rubbing against other letters with other scents. And finally, the letters were decontaminated using radiation, which might affect the scent.

Two false trails

The use of the dogs in the sniper case raised other doubts for some handlers, although the dogs apparently played no role in the identification of two suspects last week.

A Maryland law enforcement officer involved in the sniper investigation said the dogs from California, given the scent taken from spent shell casings, followed two false trails in Montgomery County.

One led to a house, for which a search warrant was obtained and which turned out not be relevant. The other led to a dog-grooming parlor, the officer said.

Others defended the Californians' work, particularly on the anthrax case. Two people in touch with FBI investigators said the three dogs were given scents taken from three different letters, and all consistently identified Hatfill while ignoring other potential suspects.

'Proud' of colleagues

Harris, the inventor of the Scent Transfer Unit, defended his three California colleagues. "Until these [critics] have tried it and tested it, they shouldn't talk about it. I'm extremely proud of these young people doing this work," said Harris, 74.

Do, the Los Angeles County prosecutor, also said the California bloodhound handlers ran tests in which they had a person touch an envelope, irradiated the envelope in the way the anthrax letters were decontaminated - and found the dogs could still track the person successfully using the scent taken from the irradiated letters.

In any case, Do said, while rules vary from court to court, nowhere can bloodhound evidence alone be used to convict a person of a crime. There has to be other, corroborating evidence, she said.

"The dog is not telling you this person committed the crime," she said. "All the dog is telling you is that the scents match. It's like a fingerprint. The fact that your fingerprint is on the gun does not mean you fired it."