The troubled history of black-white relations in Prince George's County will be brought into sharp focus today as 15-year-old Terrence G. Johnson, a black junior high school student, goes on trial on charges of murdering two white county police officers.

Officers Albert M. Claggett IV and James Brian Swart were shot and killed in the early morning hours of June 26, 1978, in the middle of the Hyattsvile police station, shortly after they had taken Johnson and his older brother Melvin, 18, into custody on suspicion of rifling coin boxes at a River-dale laundromat.

Police say that Terrence Johnson ripped Claggett's gun from his holster while the officer was fingerprinting him in a small processing room. Johnson shot Claggett in the chest, then shot Swart as the second officer ran towards the processing room, police contend.

However, chief defense attorney R. Kenneth Mundy said last week that Johnson will testify that Claggett was beating him just before the shootings.

For weeks, even before Mundy's statement, vocal groups of Johnson supporters have charged he was a victim of police brutality. At the same time, bitter police officers have repeated over and over again that it is Johnson who is on trial, and not the Prince George's County police department.

Large numbers of Johnson supporters -- drawn from church groups, neighbors of the Johnson family and District of Columbia based radical activist groups -- are expected to attend the trial, and heavy security precautions are being taken by the sheriff's department and county police.

Sherriff James V. Aluisi met with two pro-Johnson groups last week to discuss what actions the groups would be allowed to take within the courthouse in Upper Marlboro.

Every person entering the 128-seat courtroom where the trial will be held will have to pass through a metal detector, Aluisi said.

About 300 prospective jurors have been on call for the jury selection process that is expected to begin today.

Johnson, standing trial as an adult, could face two consecutive life sentences if convicted. Although Maryland does have a death penalty, it did not go into effect until July 1, five days after the shootings.

If Johnson had been tried as a juvenile, no matter what the outcome, he would have been free on his 21st birthday.

Prince George's County Circuit Court Judge Vincent J. Femia ruled last October that Johnson should stand trial as an adult, in part, Femia said, because the treatment facilities available to juveniles in Maryland were inadequate.

Johnson was arrested at the Hyattsville station immediately after the shootings of Claggett, 26 and Swart, 25.

Johnson's bond was initially set at $1,050,000. Some weeks later, Judge Jacob S. Levin, who will preside at Johnson's trial, reduced that bail to $100,000.

State Sen. Tommie Broadwater Jr. and Philip Baltimore, both bail bondsmen, put up the $100,000 bond on Oct. 17, and Johnson has been living at home in Bladensburg since that time.

Black-white relations in the county, especially between the largely white police force and the black community, have been strained for years, but have been particularly tense in the past 12 months.

The police department was severely criticized early in 1978 when two unarmed black suspects were fatally shot by white police officers. There shootings, which happened within four weeks of each other, led to charges that police were trigger-happy. After the deaths of Claggett and Swart, angry police officers contended that the police shootings proved police were in constant danger in the county.

In the meantime, rumors that members of the Ku Klux Klan might attend the trial have spurred Johnson supporters into claiming a Klan-police coalition -- a charge police angrily deny.

"No group in America is more despicable than the Klan," police union President Laney Hester said. "I would be more upset to see them at the trial than the Pro-Johnson people."

The rumors about the Klan found their way into a motion by defense attorneys. In filing a request to obtain any previous records of brutality charges against Claggett or Swart, the defense also asked for any evidence showing their membership in the Klan.

"We just wanted to check everything out," said defense co-counsel Joseph L. Gibson.

Judge Jacob S. Levin denied the request.

Now, with the trial about to start after seven months of charges and counter-charges by the two sides, everyone seems agreed on only one thing:

"No matter what happens at the trial, everyone involved has lost," said the Rev. Perry A. Smith one of the leaders of the Terrence Johnson Defense Fund. "The officers and their families have suffered and Terrence and his family have suffered. It will be a trying time for all of us."