Burtell M. Jefferson, who was one of a handful of black Washington policemen in the late 1940s, when detective assignments for blacks where severely limited and promotional opportunities all but nonexistent, took office as the city's chief of police yesterday.

He promised a continuation of his predecessors' emphasis on crime control and community relations, and said he would provide undiminished police service despite further anitcipated cuts in money and manpower.

"I am extremely proud to be afforded the opportunity to serve the people of this great city," said Jefferson. "I look forward to the challenge."

Mayor Walter E. Washington predicted Jefferson, 52, would be a "great chief," calling him "strong," "fair," and "solid," a word also used to describe Jefferson by former Police Chief Jerry V. Wilson.

The mayor noted that the District's crime rate had dropped, since 1969, fromfirst place to 17th among the nation's 20 largest cities. "I would expect that within a year, no more than a year-and-a-half, Chief Jefferson will have us at number 20," Washington added. At this, Jefferson grinned broadly.

During the 5-minute swearing-in ceremony, there was no mention of the fact that Jefferson is the city's first black police chief. That ommission was in keeping with Jefferson's own desire to minimize race and racial considerations, despite a 29-year police career during which race had long been a serious obstacle to his advancement.

Jefferson was born on Elm Street NW, in the Le Droit Park neighborhood, but spent most of his childhood living in the 800 block of 9th Street NE, not far from the old 9th precinct where he later served as a private and lieutenant.

"We were no better off or worse off than the average black family," Jefferson said during an interview earlier this week. "At Christmastime, I got toys like the other kidsskates, bicycle, sled, what-have-you."

Jefferson vividly remembered one childhood run-in with the police, when he was caught in the company of children shooting dice, and escorted home to his parents by the patrolman on the beat. That patrolman, coincidentally, was the father of retiring Chief Maurice Cullinane.

Even though Jefferson said he had merely been playing with a football at the time, he felt he deserved to be punished. "I've always on taught that if you yourself are not actually engaged in some wrongdoing, if you're with a crowd you're just as guilty."

Within weeks of his graduation from Armstrong High School, he entered the army, serving during World War II in the South Pacific and the Phillipines before his discharge in 1946. He then spent a year at Howard University, studying engineering, but quit because "I did not want to be a burden on my family," he said.

In 1948, he joined the Washington police department. After a brief stint in uniform, Jefferson worked as investigator with the U.S. attorney's office, and later with the morals division, where he was mainly engaged in enforcing the city's gambling laws.

In the mid-1950s, Jefferson and fellow investigator Tilmon O'Bryant, now the assistant chief of administrative services, organized a series of classes to help black officers, including themselves, prepare for promotional exams. "We'll figure out every possible question. We'll beat them at their own game," Jefferson is quoted in a recent biography of O'Bryant as saying at the time.

The classes were held twice a week in Jefferson's basement, and the rules were strict. No one was allowed to leave during each four-hour session. A student who missed more than two classes could be expelled from the group. Only soft drinks were served. No beer.

It took Jefferson's two procedures, Maurice J. Cullinane and Jerry V. Wilson, 20 years each to reach the department's top office. In contrast, Jefferson, who joined the department before either Cullinane or Wilson, was still a detective-sergeant when, in 1968, he completed his first 20 years as a policeman.

The riots that followed Dr. Martin Euther King's assassination in April, 1968, put sudden pressure on the city's police to recruit and promote more blacks. Jefferson's rise since then has been rapid, and for the last three years he has served, under Cullinane, as assistant chief of field operations, customarily a springboard to the chief's job.

One former sergeant, assigned to the third district at 1624 V St. NW when Jefferson was its commanding officer, characterized him as a "bookman". Another sergeant agreed, but said there has been few complaints from subordinates about Jefferson's lems.

Jefferson once banged his car into a brick wall while trying to respond to an emergency, this sergeant remembered, causing considerable amused comment among the rank-and-file because of Jefferson's reputation as a disciplinarian. But Jefferson was also widely respected for his thorough knowledge of all branches of police work, particularly investigation.

A Baptist and a regular churchgoer, Jefferson keeps a Bible on his desk. "When I first took over as inspector at the third district," he said, "Serveral of the officials and officers would look down and I'd see a funny expression come over their face."

Jefferson has not announced many specific plans for his administration, but did talk earlier this week about creating the new rank of "master patrolman."

"We have a lot of opportunities for lateral movement in the department to special assignment positions," he said. "And we lose a lot of good, efficient patrol officers because of the opportunities" elsewhere in the department.

Sworn in along with Jefferson yesterday was Bernard D. Crooke Jr., the new assistant cheif for field operations. Among those who watched the ceremony was Crooke's father, Bernard D. Crooke Sr., 75, a former homicide investigator who was a D. C. policeman from 1925 until his retirement in 1954.

Jefferson's family was also in the audience gathered at the U.S. Commerce Department Auditorium. His daughter Sheila, 25, a schoolteacher, and son Maurice, 24, a computer technician, said they had always known that their father would be chief of police one day.