Man's Best Terror Deterrent Still Somewhat-Reliable Dog

"Working dogs" also track smells for fire and police departments and search-and-rescue teams and at airports, military bases, presidential inaugurations, immigration points and major sporting events.

Some dogs are trained to find drugs or accelerants, critical in arson investigations. Others are brought in to find humans in search-and-rescue operations. "Explosives detection canines," or EDCs, sniff only for explosives.

The dogs can detect guns and ammunition hidden in containers and cars, on people and in the ground. That has made them critical in homicides and other criminal cases, including that of the Washington area snipers, when dogs located shell casings.

A dog's nose is 100 to 10,000 times more sensitive than the human nose, depending on the odor, said Paul Waggoner, director of the Canine and Detection Research Institute at Auburn University. A dog has about 1 billion olfactory receptors, compared with roughly 40 million in humans, he said.

"They smell everything separately, where we only smell the strongest odor in the room," Fry said. "If beef stew is cooking, we smell the stew as a whole. But the dog smells the beef, the carrots and the potatoes separately. If there's one pea in the stew, the dog will know it's there."

Andy enrolled at the Canine Enforcement Training Center in Front Royal, Va., for six weeks of classic Pavlovian conditioning with explosives. His personality was then "matched" with Fry, an ATF agent for 13 years who grew up on a farm in Minnesota and loves animals. The two went through 10 more weeks of training to cement their relationship. They live together, and, each year, Andy is retested and recertified by the ATF.

But some dogs have not been trained so rigorously. Two years ago, a federal judge imposed a 6 1/2 -year sentence on a Hagerstown, Md., man who provided the government with bomb-sniffing dogs that could not reliably smell explosives.

The dogs failed a "covert operational test." When federal officials drove past them in cars loaded with 50 pounds of dynamite, 50 pounds of TNT and 15 pounds of plastic explosive, the dogs "didn't so much as sneeze," jurors were told.

Staff writer Mary Jordan reported from London. Staff writers Lyndsey Layton and Laura Blumenfeld also contributed to this report.