Wearing a hidden microphone and pretending to be a heroin addict, an undercover D.C. police detective penetrated an alleged crime ring last fall and made a half-dozen clandestine deals aimed at smashing the gang. But the officer was not investigating drug dealers.

Rather, the detective and other investigators were painstakingly building a case that a group was selling stolen property out of an auto body shop on Kalorama Road NW.

Over several months, the thieves gave the undercover officer lists of desired items: laptop computers, digital cameras, camcorders. Within days of each request, the detective returned with the goods. When police raided the business in November, detectives said they found boxes stuffed with stolen electronics waiting to be shipped overseas.

The investigation was just one of a half-dozen recently conducted by D.C. police during a rare crackdown on groups, known as fences, that traffic in stolen goods.

In court documents and interviews, police provided a window into how fences have evolved, growing more sophisticated and no longer relying on the walk-in traffic of burglars. Fences hand out "shopping lists" to thieves, give tours of target neighborhoods and now pull loot from burglaries and thefts across the Washington area into their District-based operations.

Some groups also have begun to dabble in identity theft, asking bandits to target credit cards and checkbooks. And, police said, the stolen items are not just being peddled out the back door or on sidewalk stands. With the help of the Internet and overnight shipping, the fencing operators are sending stolen goods worldwide.

The developments could have broad implications for law enforcement in the region as police try to reduce property crime. In the District, police recorded nearly 5,000 burglaries and 16,890 thefts last year. Across the Washington area, police reported more than 25,000 burglaries and 118,380 thefts in 2002, the last year regionwide statistics were available.

Many of those crimes are committed by neighborhood teens or other residents who pocket the stolen items themselves. Other thieves continue to make quick sales to pawn shops.

But District and suburban police said a sizable chunk of stolen items is being funneled through fencing operations. Career burglars often strike house after house, or store after store, to get enough cash to satisfy their drug addictions. Often, those burglars get away with 30 or 40 thefts before being caught.

In Montgomery County, for example, police said drug addicts were responsible for many of last year's 4,095 burglaries. Those thieves often sold their goods in the District to fencing groups.

"A lot of it goes downtown, and we know a lot of our drug-related crime goes right back to the District to be sold," said Lt. Michael Mancuso, who heads Montgomery's criminal investigation division, adding that his detectives were investigating several fencing operations that have sprung up in the county.

Fencing stolen items is an age-old practice of burglars. Yet just a few decades ago, fencing operations generally fell into three categories: pawn dealers, mom-and-pop businesses and organized criminal groups, such as La Cosa Nostra and the Russian mafia. Authorities said newer fencing operations hide from sight in legitimate businesses and show discipline and precision in their dealings.

To break up the gangs, D.C. police have been forced to undertake months-long undercover operations, complete with confidential informants.

"If these groups were not good, we wouldn't have to put so much effort into taking them down," said D.C. police Detective David Swinson, who leads the city's initiative targeting the rings. "It's very similar to a drug gang, the way they operate. These organized fencing operations know their market."

Across the country, law enforcement officials report groups of criminal middlemen employing bands of burglars to target businesses and homes, in some cases providing burglars floor plans and maps of their targets, according to interviews and court records. Other fences have created platoons of shoplifters to strike retail stores. Some are working with bands of hijackers who hit trucks and trains carrying expensive cargo.

D.C. police and prosecutors said they think that the crackdown in the city has had an impact. Through the first six months of this year, burglaries declined 16 percent in the District. They dropped 25 percent in the 3rd Police District, which covers much of downtown and several "target rich" residential neighborhoods such as Adams Morgan and Dupont Circle, police said. Many of the city's fencing investigations began in the 3rd District.

"It breaks the market, and suddenly the highway isn't smooth anymore," said Assistant U.S. Attorney Bruce Hegyi of the transnational and major crimes unit, who is handling some of the first cases brought by D.C. police, in part because of the global reach of the fencing enterprises. "They have to look and find somewhere else to go."

The D.C. crackdown began last year when Swinson, a veteran property crimes investigator in the 3rd District, arrested several burglars who began tipping him off to fencing operations. The burglars, who often did not know one another, had learned about the fences through gossip on the street. Then they became regular patrons of the fencing groups.

As he began to tackle the fencing operations, Swinson soon realized that the investigations took too much time for one detective. He added two others to his team: veteran Detectives Joseph Radvansky Jr. and Neil Jones, who have specialized in tracking down serial burglars. To help finance his effort, Swinson obtained a $10,000 grant from the National Capital Police Fund, an initiative of the Federal City Council, a nonprofit group of influential business leaders.

A burglar first pointed Swinson to a group operating out of J and N Auto Service in the 1700 block of Kalorama Road NW, a concrete-block building on an otherwise quiet residential street in Adams Morgan.

In September, U.S. District Court records show, police sent a confidential informant into the auto shop and sold an employee "bait" property. Within a few weeks, the informant brought an undercover officer in on the deals, which were recorded by a hidden microphone. Other police officers kept careful watch on the deals from a vehicle hidden nearby, investigators said.

Soon, the undercover officer was making regular visits to the auto shop to sell stolen goods, police said.

Within a few visits, the shop's employees were giving the undercover detective a detailed shopping list of computers, electronic goods, jewelry and other items, police said.

When Swinson and other detectives raided the shop, they discovered several large boxes stuffed with electronics items to be shipped to Central America, police said.

Police eventually charged three employees with stolen-goods trafficking in U.S. District Court. One has not been caught, and another is wanted on a warrant issued by a judge for skipping a court date, authorities said.

The third is awaiting a trial date. Police said the owner of the shop, Nery Orsco, was not involved in the ring. Orsco, who was hospitalized for an illness during the investigation, said he was "disappointed" by his employees' actions.

In a similar undercover investigation last year, police arrested an employee of a newsstand that sold an assortment of magazines, chewing gum, candy, sodas and pornography in Northwest Washington. Behind that business front, the man was actually specializing in fencing camcorders, digital cameras and laptop computers, according to police and a nine-page affidavit filed in D.C. Superior Court. The case is awaiting trial.

As in the auto shop investigation, the defendant told police he was shipping the laptops, CDs and other goods overseas, the affidavit alleged.

In May, police and U.S. Secret Service agents raided a gas station in Northwest Washington that they alleged was a front for several fences trafficking in laptops and stolen credit cards, authorities said.

To crack the gang, investigators sold one suspect fake credit cards and charted the purchases. Some of the charges occurred within minutes of the undercover sale, police said.

Two months ago, police raided two fencing operations in Southeast, one operated from a pizza shop and another from a Chinese restaurant, according to Superior Court records.

During one recent transaction at the Chinese restaurant between an employee, an undercover detective and an informant, the employee complained that he couldn't sell one of the laptops sold to him because he couldn't cleanse its hard drive, police said.

In the future, police said, the suspect demanded that the thieves' computers be wiped clean.

"I don't care about the software," the suspect told the informant and officer, according to charging documents. "I can get any kind of software I want. I can't have [any] traces of previous users account files whatsoever."

The minor snag did not seem to diminish the suspect's enthusiasm for his trade, however. Before the informant and undercover detective left the restaurant, the charging documents state, the suspect quickly put in another order with them. He wanted as many laptop computers as possible, he said, and would pay $350 for each, so long as "they were top of the line."

Gloria Borland stops by 3rd Police District headquarters with daughter Imiloa, 2, in search of items stolen from her D.C. home. She did not find any of the $14,000 worth of items taken.D.C. police Lt. Robert Glover completes the paperwork that will allow Sherry Harper to get back her stolen earrings. Authorities in the District have recently investigated a half-dozen groups that traffic in stolen goods.A gold pocket watch is one of hundreds of pieces of stolen jewelry confiscated by police. A property viewing at the city's 3rd District headquarters included items recovered from a fencing bust at an auto body shop in Northwest Washington. Detective David Swinson shows Kathy Kelley stolen items confiscated by police. Kelley had computer equipment stolen from her home.