They've been finding hidden bombs, drugs and corpses for years, using their sense of smell to locate what their human handlers would otherwise have to see in plain sight.
Now dogs are being deployed in prisons to help curb one of the most serious problems confronting corrections officials: smuggled cell phones.
It turns out that cell phones smell. And their distinct odour can lead a well-trained canine to a device hidden under a mattress, stashed into a wall or tucked into a fan or radio.
Inmates use them to arrange drug deals, plot escapes and attacks, coordinate riots and harass victims.
"They have 24 hours a day to figure out how to hide these from us," said Sgt. Wayne Conrad, who leads the K-9 program in California. "I couldn't tell you how long it would take me to go through every nook and cranny in a cell. But when these dogs work, they pick up the odor and go right to it."
For security reasons, Conrad won't say what the scent is, but says dogs can find it whether the phone is on or off, broken into pieces or concealed in another electronic device.
Cell phone sniffing dogs have been dispatched in prisons in a handful of states, including California, Florida, Texas, Virginia and Maryland, as other methods to heel the problem have fallen short or run into regulatory or budgetary constraints.
There are currently 14 dogs working in California's 33 prisons. Five of them are specifically trained as cell phone sleuths. By the end of the summer, the K-9 unit will have 23 dogs trained, about half in finding cell phones, the other half in narcotics.
The program continues to grow despite California's $19 billion budget deficit because it's cheap: the dogs are donated by rescue groups and trained onsite for eight weeks at a facility in Galt, about 20 miles south of Sacramento.
As of May of this year, California prison officials had already confiscated 4,800 cell phones through the K-9 program and other random searches. They seized nearly 7,000 last year, up from just 261 in 2006.
Cell phones are smuggled into prisons through visitors and staff. They're stuffed in cakes, hidden in hollowed out books, thrown over prison walls in garbage bags, transported in laundry delivery, broken apart and brought in bit by bit and disguised as wristwatches or radios.
"They have hidden them inside a body cavity," Conrad said.
A smuggler can fetch up to $1,000 for a phone, and prisoners rent them out to other inmates for $50 a day, said Richard Subia, California's associate director for adult prisons.
California lawmakers recently passed legislation that would make cell phone smuggling a misdemeanor and fine the offender up to $5,000. The bill is currently on Gov. Arnold Schwarzenegger's desk.
The U.S. House last month passed a bill that would ban the use or possession of cell phones or wireless devices in federal prisons and classify those devices as contraband. The U.S. Senate also has passed a similar bill, sponsored by California Sen. Dianne Feinstein, who noted that one fired guard admitted making close to $150,000 in a year smuggling cell phones. The legislation would subject anyone trying to provide a cell phone to an inmate to up to a year in prison
Concerned about safety, more than 20 states last year petitioned the Federal Communications Commission to allow them to jam cell phone signals at state prisons. The high tech solution is currently prohibited because any disruption would also affect neighboring communities.
"So that's when it came back to dogs," Subia said. "We found our resources weren't enough to keep up with the discovery of cell phones."
Another problem is that cell phones are getting smarter, and their uses more sinister.
"Inmates take pictures of security procedures and drills and send them to people on the outside," Conrad said. "Sex offenders communicate with young kids by posting videos on YouTube and MySpace. This isn't just about safety in prisons. It's safety for the outside, too."
At a recent training demonstration, Conrad and another handler, Brian Pyle, brought 7-year-old Caesar and 2-year-old Drako into a mock prison dorm to search for contraband. To the dogs, Belgian Malinois, it's all fun and games.
They search for their toy, and when they find it, they bark at it, bite and scratch.
Caesar goes first and locates a phone tucked into a vacuum. Drako finds a phone hidden in a light socket.
Taking turns they go across the room and uncover phones under mattresses, in shoes, in a VCR, in a locker.
The door to the demonstration is shut so inmates working on the grounds don't see the dogs in action. Nevertheless, their reputation has spread beyond these walls.
"We did a random search at a prison one day and when we started coming toward the dorm with the dogs all these phones started flying out the windows," said Conrad.
The dogs are apparently having an effect. And in that case, they didn't have to smell a thing.