A man was suspected of filling narcotics prescriptions without a pharmacist's license, and Maurice Evans was encouraging the young undercover investigator who would help him make the bust.

"I'm gonna give you a prescription for Percodan. It's already got your name on it. All you gotta do is get it filled," Evans prompted.

Three hours later, the suspect was in a cell at the 4th District police station, and the District pharmacy's records and drugs had been seized.

The investigation was routine for Evans, but he is no police officer. A member of the District Department of Consumer Regulatory Affairs investigation team, Evans is a detective of another kind, the consumer advocates' Mike Hammer.

Charged with catching violators of the city's consumer protection laws and regulatory guidelines, Evans is part of a 23-member unit that last year investigated more than 4,000 cases.

On occasion they have teamed up with the U.S. Postal Inspection Office, Federal Trade Commission and the FBI.

But more often than not they are on their own, tracking down those who take money from the unwitting, break contracts and impersonate licensed professionals. There are enough of them to "keep us in business," Evans said recently.

"They are out there investigating, collecting evidence and ensuring that the people they are charged to regulate are operating within the requirements of the law," according to police Lt. Michael Elmore of the city's repeat offenders unit, an elite squad that often works with Evans and others from the city's Consumer Regulatory Affairs agency.

The investigators operate out of the department's headquarters at 614 H St. NW. Three years ago, the department was organized to consolidate eight small regulatory administrations and 22 boards and commissions that oversaw various consumer interests. More than a third of the investigators' work stems from more traditional consumer complaints about problems that range from the sale of counterfeit Cabbage Patch dolls to shoddy work by auto dealers and home repairmen.

Those kinds of complaints come to the investigators if they cannot be mediated first by the department's consumer complaint office.

Eloise Wade, a 25-year District resident, contacted the department about a travel agency's refusal to refund money for a trip she never took, despite its promises that she'd get her money back. The complaint was turned over to the investigators who spent several days tracking down the elusive travel agent, according to Wade. Their work resulted in an administrative judge's decree a year later that Wade was due a $1,200 refund, plus interest.

"They sent out an investigator and spent a considerable amount of time and resources," she recalled recently, adding that the investigation was "slow but consistent."

The speed with which the investigations are conducted is a major complaint against the agency.

"The consumer is our main critic," according to Betty Faison, acting investigations chief. "The consumers expect something to happen in a week and it takes longer than that."

Department officials acknowledge, however, that after the 1983 merger a backlog of cases caused lengthy delays. District law requires that consumer complaints be handled and reasonably resolved within 180 days of a formal complaint, but some consumers waited as long as a year before their complaints were even looked into.

According to Faison, a former District police officer, each investigator in the newly formed unit at first had to juggle up to 100 cases because of the workload created by the merger.

At least 10 new investigators have been hired since then, and each investigator now has a load of about 25 cases, she said.

The unit also gets cases that have not been resolved elsewhere in the Consumer Regulatory Affair's agency, such as those involving insurance, professional and business licensing.

Their jurisdiction and authority is broader than those of most local consumer agencies, which generally resolve cases by negotiating settlements and issuing consent orders in which a business agrees not to break consumer laws. In the District, consumer agents have the additional power to close businesses, revoke licenses and seek criminal penalties.

While Evans and his colleagues carry no weapons and rely on police to make arrests, they say they can be more effective than typical law enforcement officers in certain situations.

"Police can come in a place and arrest people for prostitution and they're back the next day," said Evans, "but we close your business down."

Last year, when citizens complained about activity at The Godfather club on Wisconsin Avenue, operated by sex entrepreneur Dennis Sobin, the agency shut it down.

Undercover investigators witnessed sexual acts on stage and decided the club was violating licensing regulations, according to Faison. "It didn't have a certificate for a sexually oriented business," she explained.

Often those who violate consumer protection laws violate criminal ones as well. The investigation of the pharmacist arrested last month at Surgical Apothecary on Georgia Avenue, for example, was initiated after the agency received a tip that the man was not licensed.

Fourth District police arrested and charged James A. Marshall of Pomfret, Md., with illegal distribution of a controlled substance, a felony. The arrest was made after Evans and investigator Sharon Humphrey filled a prescription at the pharmacy.

A Boston University political science graduate, Evans, 30, is among a group of lawyers, paralegals, former police officers, a social worker and a former Foreign Service officer who comprise the consumer investigation unit, where the average salary is $22,000.

Frequently the investigators don't wait for complaints to come to their office.

When a tenant who shot and killed an eviction crew member publicly complained that he did not know his house had been taken over by a loan company, the investigators began seeking out others with similar experiences.

Rita Walker and Ferris W. Browner, officers of the loan company, were ordered last month by a D.C. Superior Court judge to pay a total of $9,000 restitution to three consumers after being convicted of unlicensed money lending and operating a business without a license.

Going after cases on their own is important, the investigators say, because many consumers are unaware when they have been victimized.

According to Fred Johnson, the acting assistant chief, "There are a lot of people who don't even know they're being ripped off."