The D.C. Police Department had almost given up on finding the river of the car that struck and killed 11-year-old Delonte Butler as he bicycled to a carnival near RFK Stadium last May. Police found the car, but came up with only weak description of the driver: a black male in his teens.

This was a job for Crime Solvers.

Police took the case to the community, offering cash rewards for information that would lead to the arrest and indictment of suspects involved in the hit-and-run fatality.

And within days, the calls starting coming.

"There was lots of talk on the streets," said Renne Sanjurjo, coordinator for the D.C. Crime Solvers program. "Kids in the neighborhood heard it and called in."

As a result of the tips, police picked up two suspects. One neighborhood youngster was given a $1,000 reward and three others were awarded $200 each for the information that led to the arrest of the suspects, who were later convicted.

In the Crime Solvers program, police offer cold cash supplied by local businesses to the public in return for hot tips on cases where leads have run dry. The tipster is guaranteed anonymity, but before he can collect, the information must result in an arrest and indictment.

Over the past four years, Crime Solvers has become an increasingly important tool to Washington area police. Almost $100,000 in rewards has been paid out to anonymous tipsters through Crime Solvers programs run by police in Alexandria, the District and Fairfax, Montgomery and Prince George's counties, police records show.

District Crime Solvers has paid $4,600 in rewards to 16 anonymous sources since it opened its telephone lines 16 months ago. The D.C. program has fallen short of its suburban counterparts in the number of cases it has helped police close.

But Sanjurjo said the program, which has received 500 telephone tips since it started, is only recently becoming well-known in city communities. And while suburban programs can turn to almost a dozen local weekly and biweekly newspapers for publicizing their unsolved crimes, Sanjurjo said the D.C. police have to rely on a much smaller pool of neighborhood newspapers.

In Fairfax, Crime Solvers has paid $29,700 over the past three years for information that police say has helped close 303 cases and recover $301,153 in stolen property. The fledgling 11-month old Alexandria program, the newest in the area, has paid $3,900 to anonymous callers who helped police close 70 cases and recover $40,000 in stolen property.

Leslie Harris, executive director of the Capital Area office of the American Civil Liberties Union, said she has received no complaints about misuse or abuse of the Crime Solvers program, but that such programs "have to be very carefully administered. Peoples' private interests are at stake.

"Anytime that there is a collection and maintenance of information about citizens, there is a question of how that information is being used . . ." Harris said. "But I have received no complaints about the use of the Crime Solvers program. The government always has an obligation to use information from the public in a very careful manner."

Only a small percentage of the callers actually receive rewards, police records show. Fairfax Crime Solvers, for example, has paid 85 tipsters in the past three years--about 5 percent of the 1,623 calls logged in that period. In Alexandria, only 11 of this year's 123 callers received rewards.

The money used for rewards is donated by businesses and civic groups. Police departments provide only the manpower used to operate the Crime Solvers telephone lines and research the crimes. A civilian board, composed primarily of local business leaders, decides how much each caller will be paid.

Members of the civilian boards of directors also arrange the actual payoffs to informants, who are recorded by number, not by name, when they call. In fact, the informants are never seen by a police officer, police say.

A typical payoff might take place at a local grocery store, where the informant would ask for the board member by name while the board member would know only the informant's assigned number. After the identification had been completed, the reward would be paid.

Police concede that much of the reward money goes to criminals and friends of criminals. Callers frequently are partners in crime who feel they were cheated out of their fair share of the take, police say.

"We find a lot of the people calling are involved in crime themselves or know the people who are involved," said Sanjurjo.

Fairfax Crime Solvers coordinator Richard D. Crosby describes his typical anonymous caller: "They want their bucks. They're speaking in hushed tones. They may even be in the same house of the person they're turning in."

Girlfriends snitch on boyfriends, neighbors turn in neighbors, wives report husbands. A woman in Fairfax, angry that her husband hadn't come home in four days, called the Crime Solvers line to report that he was making PCP. She sent police to the location, where her husband was arrested and the PCP was confiscated. The wife later collected the reward.

Or take the case Montgomery County Crime Solvers coordinator George C. Heinrich took two years ago. The state of Alaska had shipped a team of prize-winning husky dogs to Washington for President Reagan's inaugural parade, only to have three of them stolen from the Damascus farm where they were penned the day before the parade. Police had no leads and members of Congress were demanding fast action.

Police took the case to the television station that aired a "Crime of the Week" series and offered a $500 reward for information on the whereabouts of the huskies, which were valued at $5,000 each.

A few hours later, a woman called police to report she'd discovered the dogs in her basement. She turned in her two sons, who were charged with larceny. The mother collected the reward and the huskies made it to the parade on time.