Terrence G. Johnson took the witness stand in his own defense yesterday and testified that he believed Prince George's County police officer Albert M. Claggett IV "was going to kill me" seconds before he wrenched Claggetths gun from its holster and shot and killed him last June 26.

The 16-year-old Bladensburg youth on trial for the murders of Claggett and his fellow officer, James Brian Swart, also told the jury that he and Claggett had been struggling and that Claggett had locked an arm around his neck when Johnson grabbed the officer's gun.

Then, at the prompting of his defense attorney, the slight black youth stepped down from the witness stand and reenacted the final seconds of struggle that culminated in the double slaying in the Hyattsville police station -- an act that has heightened volatile racial tensions in the county.

"He had his arm around my neck," Johnson said, ducking his head under the arm of a county police officer who was taking the role of Claggett. "I slipped free for a second and bit him on the chest. He kneed me and I went onto the desk.

"He yanked me down and started squeezing me real tight.

"I yelled 'aaah,' cause it hurt and he said, 'Shut up, nigger.' He was still squeezing when I just reached around and yanked."

But during the reenactment, which came halfway through the youth's 2 1/2 hours of testimony, Johnson stopped short of grabbing the empty gun from the officer's holster. "When I got the gun, he said, 'Why you black m ' and he lunged for me. The gun went off. I saw red spots on his shirt. He curled up" -- Johnson doubled over to demonstrate -- "and just looked at me with his eyes wide open.

Johnson's wrenching testimony came as the emotional trial entered its second week in Prince George's County Circuit Court in Upper Marlboro.

Earlier in the day, before Defense Attorney R. Kenneth Mundy began to president his case, presiding Judge Jocob S. Levin called both prosecuting and defense attorneys into his office and asked them to try to negotiate a legal compromise to end the trial.

After half an hour of futile plea bargaining, Statehs Attorney Arthur A. Marshall Jr. and Mundy told the judge they could not agree, and returned to the courtroom.

Before calling Johnson to the stand, however, Munty asked the youth's older brother, Melvin Kevin, to testify. The 19-year-old then provided some of the most confusing testimony of the trial.

Contradicting every other witness caled for both the defense and the prosecution, Melvin Johnson said that, as Claggett took Terrence into the small fingerprinting room where the shootings began, a second officer, Paul J. Jahn, joined them.

Melvin Johnson said that shortly after his brother, Claggett and Jahn went into the room, Terrence came out with a gun in his hand and fired two shots, which went over his (Melvin's) shoulder, then ran from the room.

"A few seconds later officer Swart ran into the room and glanced at me," Melvin Johnson said. "Then I heard another gunshot. It didn't come from the hall."

"Are you telling us that your brother did not shoot officer Swart?" Marshall asked. "Yes," Melvin Johnson answered.

Melvin Johnson also testified that he had a feeling when Claggett was driving him to the station that "something bad was going to happen to him for picking us up." Asked by Marshall how he knew, Johnson said, "through ESP," which he contended everyone has.

Mundy said later that the contradictions between Melvin's testimony and other witnesses' had hurt Terrence Johnson's case.

Terrence Johnson's subsequent testimony was radically different and conformed far more closely with the defense's version of what happened in the basement processing room of the police atation.

Johnson said he was at home talking to his girlfriend on the phone at around 1:45 a.m. -- he later said it was closer to midnight -- when Melvin arrived, announced he had broken into a coin machine and suggested they go to the movies.

The two were stopped by four police officers on Rte. 202 shortly after leaving, Johnson said, and it was Swart who insisted on arresting him instead of sending him home since he was 15 at the time.

Johnsondenied giving Swat a hard time, as police witnesses had testified, while handcuffed to a chair in the processing room.

"I did what he told me," Johnson said, speaking in a low voice as he did throughout his testimony. "Once, when I leaned over, he said, "Get back, your breath stinks,' and then he kicked me back.

"I said, 'Officer you don't have to be doing that," and he kicked me in the groin and then punched me in the face. I stood up with my chair and tried to swing it and he grabbed the chair and I fell.

"Before I hit the ground, though, officer Claggett came up behind and grabbed me by the back of my neck and said, 'I'm going to break your little neck, and put his knee in my neck.

"Then they held me down in the outer room like that for about a minute or a minute and a half. Somebody hit me in the side and my face. Claggett said to someone, 'Take the cuffs off,' and slammed my face into the wall.

"Then he picked me up and pushed me into the (fingerprinting) room."

At that point Mundy asked Johnson to demonstrate what happened in the room and he did so, with the officer helping him reenact the struggle with Claggett, Johnson, however, stopped at the moment he would have grabbed the gun.

Under cross-examination, however, Marshall insisted that he continue the reenactment. The prosecutor stood next to Johnson and yelled, "pull it out! pull it out," when the youth reached the point in his story when he said he took Claggett's gun.

Johnson was calm throughout the direct testimony but during Marshall's tigerish hour-long cross-examination finally broke down and cried when Marshall angrily grabbed Claggett's gun from his hands when Johnson said he could not remember how he had held it while shooting Claggett.

Despite Marshall's haranguing and yelling -- the prosecutor was told several times by Levin to get his face away from Johnson's -- the youth did not change his story or his low-key tone.

The same was not true for his brother, who told Marshall that he repeatedly lied to detectives about what he had seen in the processing room because, "I was afraid they would kill me if they thought I knew anything about what happened in the station."

The testimony of Melvin Johnson left the defense noticeably opset and discouraged.

"I thought about not putting him on but then Marshall would have jumped on the fact that we were afraid to call his [Terrence's] own brother.That would have hurt us, too."

However, Mundy said that Terrence Johnson "did well" on the stand.

After Terrence Johnson tinished on the stand, Mundy briefly called his mother, Helen Johnson, who testified that Terrence came from a broken home. Her voice was barely audible, even with a microphone.

The long day also produced the first flare-up among spectators warching the trial. Knowing that Johnson was going to testify, his supporters arrived early and in larger numbers then any tim previously in the trial.

According to sherriff's officials, one man was arrested on trespassing charges after he refused to wait in line, insisting he be let into the packed courtroom even though about 100 people were ahead of him, and then refused a deputy's request that he leave the building.

Perhaps the mood of the trial, which now is expected to end Thursday, was best summed up by Levin, when one of the lawyers noted this was the seventh day of the trial. "No." Levin responded, "this is the sixth day we've been here. It just feels like 60."