D.C. Police Chief Burtell Jefferson, under pressure from Mayor Marion Barry and his own homicide squad, appointed a three-member panel yesterday to investigate charges by the detectives that Deputy Chief William Trussell is "incompetent" and has made racial slurs.

Jefferson's unusual action was a victory for his openly rebellious homicide detectives, who had refused to meet with Trussell yesterday morning to discuss their complaints that his "interference" had jeopardized several major unsolved homicide cases.

Jefferson ordered the panel, made up of two senior black officers and a white police department attorney, to immediately begin investigating charges that Trussell, who is white, made a remark equating blacks with animals.

A separate investigtion of detectives' charges that Trussell has violated police procedures repeatedly in investigations will begin later, Jefferson said.

Detectives quote Trussell as having said on two separate occasions to white detectives: "Not all people go into shock. Animals don't go into shock when they are shot, and neither do blacks." Trussell has declined to either confirm or deny that he made the remark.

At a news conference yesterday morming Jefferson said, "In looking at the allegations remarks being made was the most serious."

Jefferson said that Trussell, 51, a 29-year veteran of the force and commander of the Criminal Investigations Division, "is still the chief of detectives and will remain so" until the investigations are completed. The policemen's union had called for Trussell to be suspended.

Jefferson said that Trussell has already given him a written response to the racial charges and that Trussell has been directed to prepare a written response on the other charges as well.

High-ranking aides to the mayor said Barry was "distressed" by some aspects of Jefferson's handling of the Trussell controversy. Barry was particularly upset, they said, because in failing to resolve the controversy quickly, Jefferson opened the door to possible intervention by members of Congress who were approached by detectives.

"He was not pleased with the fact that they felt they had to go to the Congress. There's supposed to be channels within the department," said one aide to Barry, who asked not to be named. "That does not help our cause any when we call for autonomy by showing we can handle our own affairs."

One of Barry's closest advisers, asked yesterday if the invitations for congressional intervention had affected the city's case for more self-government, said simply, "It didn't help." The aide said, "Different people have different ways of doing things. I would have done it differently."

Barry had said in the past that he believes the city government must demonstrate the ability to handle its own affairs effectively if it is to press its case for greater home rule. The fact that the city government is preominantly black, Barry has said, creates even more pressure for effective city management.

Ever since the controversy threatened to break wide open, Barry and some of his top officials have been conducting a behind-the-scenes effort to push Jefferson to get the worsening dispute under control.

Jefferson said yesterday that Barry had personally approved his action. It was learned that Barry told police union officials Tuesday night what Jefferson was going to do. The union was one of three major labor groups to support Barry's mayoralty campaign last year.

Barry also repeatedly telephoned Jefferson about the dispute and at one point considered attending a meeting on Monday between Jefferson and the dissident homicide detectives. The sources said Barry decided he would be a disruptive influence and let Jefferson handle it alone.

The three members of the panel appointed yesterday are:

Assistant Chief Maurice Turner, 43, recently appointed field operations commander, the No. 2 post on the force. Turner is frequently mentioned within the department as a potential successor to Jefferson as police chief.

Deputy Chief Marty Tapscott, 42, a 20-year veteran who also was recently promoted. He will become an assistant chief on Friday, taking over Turner's old job as head of administrative services.

Deputy general counsel Richard Brooks, 38, who joined the department's legal staff in 1974 after working in the New York law firm of Louis Nizer. He also has served as senior law clerk to U.S. Court of Appeals Judge Spottswood Robinson.

Brooks is white. Turner and Tapscott are black.

Jefferson said he chose Turner and Tapscott because "both have past investigative experience as well as management experience. . . . That way I thought a fair and impartial investigation could be conducted by them."

The homicide squad detectives charge that Trussell lacks investigative experience to direct or personally join in homicide cases.

Jefferson said he chose Brooks for "balance." "I felt . . . there should be a person who would be unbiased . . . from one particular area [of management or investigaions], together with the fact that he has legal background."

The panel met the approval of the homicide squad, the policemen's union and Trussell. "I am totally confident of the abilities of the panel," Trussell said after the announcement.

Trussell was given until next Thursday to complete his written response to three pages of detailed charges leveled by the homicide detectives.

The panel members, who have been relieved of their other duties during the investigation, will begin the complicated review of the detectives' "police procedure" charges after they have made a report on the racial slur, Jefferson said.

Jefferson did not give the panel members deadline to report on their findings, but strongly indicated he wanted an immediate resolution of the racial charge.

The panel began calling individual members of the homicide squad who said they heard the remark to a closed meeting yesterday afternoon.

The turmoil over Trussell's leadership erupted last week after Trussell's abrupt transfer of veteran homicide Lt. Raymond Pierson. Forty-two of the 45 squad members signed a letter expressing "collective rage" and saying the department was being run by "whim instead of reason."

It was the catalytic event that touched off an outpouring of publicly made complaints had been growing against Trussell. The complaints had been growing since September, when Trussell was appointed by Jefferson as head of the criminal investigations division.

In addition to the alleged racial remark, Trussell was accused of jeopardizing three major cases: A triple slaying in Southeast Washington last September, the February murder of a Capitol Hill woman in her home and the drowning death of a 5-month-old Swedish baby in the Capitol Hilton Hotel last month. CAPTION: Picture 1, Police Chief Burtell Jefferson: "I felt that the charge of racial remarks . . . was the most serious." By Larry Morris-The Washington Post; Picture 2, DEP. COUNSEL RICHARD BROOKS; Picture 3, ASST. CHIEF MAURICE TURNER; Picture 4, DEPUTY CHIEF MARTY TAPSCOTT