A Prince George's County Circuit Court judge ruled yesterday that 15-year-old Terrence G. Johnson must stand trial as an adult on charges of killing two county policemen, rejecting defense arguments that Johnson acted "as a 15-year-old child scared out of his wits."

The intention of defense lawyers to try to prove that Johnson acted in self-defense became evident during the final moments of a 14-hour hearing that ended at 3:47 a.m. yesterday. Judge Vincent J. Femia decided Johnson should face trial in adult court on charges of killing Albert M. Claggett IV and James Brian Swart inside the Hyattsville police station on June 26.

The ruling means that Johnson, if convicted, could face life imprisonment rather than being released from the custody of the court at the age of 21 under the juvenile court system.

In making his closing statement, chief defense attorney R. Kenneth Mundy revealed what he called "our version" of the events in the Hyattsville police station to the judge and about 75 spectators left over from the approximately 200 people who were on hand when the hearing began.

Referring to a report written by a psychiatrist, Dr. Richard Rattner, Mundy said, "Terrence indicates that he was handcuffed to a chair and subjected to verbal abuse. When Terrence responded, the officer [Claggett] tried to kick him in the groin and then cursed him.

"Then Terrence was told he would be taken into the back room to have his neck broken. This was not a case of a young man who took a gun on the street looking for someone or someone who was bent on committing a crime.

"Terrence was arrested for an extremely minor offense [suspicion of breaking into a laundromat coin box]. He had no hard attitude towards crime.

"When he acted in that police station he did so as a juvenile who was scared to death."

Mundy's dramatic speech was the culmination of a day that began with about 70 Johnson supporters singing songs - "We all know it's plain to see, Terrence Johnson must be free," - and chanting while waving "Free Terrence Johnson," flags.

It ended with Johnson, his family and defense team of six lawyers quietly leading those supporters who remained out of the courtroom at 4 a.m. moments after Femia ended a 50 minute speech by announcing that Johnson would be tried as an adult.

Before announcing his decision to deny the defense motion to wave Johnson to juvenile court, Femia carefully went over the five criteria used in making a ruling on waver - age, mental and physical condition, amenability to treatment in the juvenile justice system, the nature of the crime and potential danger to the community.

Femia gave detailed reasons for perceiving Johnson to be an adult according to most of the criteria involved, then launched into a fierce diatribe system. "The system is a tragic failure.

"Is Terrence Johnson amenable to treatment in a juvenile facility?" Femia asked. "I believe he would be. But in the state of Maryland? No chance. There is no place for him in the juvenile system . . . We have no place for the Terrence Johnsons."

Earlier in the hearing, State's Attorney Arthur A. Marshall Jr. produced a parade of witnesses who testified to problems Johnson had experience at school. "We have heard consistent testimony as to the explosive nature of Terrence Johnson and his antisocial conduct," Marshall said. "We have heard of his inability to cope with authority.

"And," he added, "there are two policemen dead in Prince George's County. That alone speaks of the nature of this crime."

Defense attorney Mundy, who called only three witnesses, tried to make his case by pointing out inconsistencies in testimony from state witnesses and trying to prove that Johnson's run-ins with teachers represented "childish acts."

Mundy pointed to Johnson's parole and probation report, which, although it recommended that he be tried as an adult, described him as "immature."

He also said that Johnson's teachers' descriptions of his recurrent behavioral problems at school were "examples of childishness."

Throughout the hearing, which Femia was determined to finish in one day so he could leave for vacation on schedule yesterday Femia sparred with Mundy. First Mundy asked Femia to diqualify himself because of his frequent statements on the need for stricter juvenile justice.

That motion was denied, as was a defense request that the courtroom be closed to the public.

Johnson was initially charged as an adult under a Maryland law that requires that juveniles between 14 and 17 be charged as adults if they are accused of a crime that carries a penalty of life imprisonment.

This is in contrast to Virginia law, which requires that anyone under 18 be charged as a juvenile and be treated as such until and unless a judge waives them into the adult system for trial.

The most dramatic testimony of the long night came from the state's final witness, county police officer Steven J. Roberts.

In what appeared to be a prelude to the state's case, Roberts testified that he saw Johnson enter the station along with his brother Melvin, who had been driving around Hyattsville with Terrence when the two were picked up by police.

"Shortly after that I hear a disturbance in the processing room," he said. "When I went in I saw Terrence Johnson being held to a chair by two officers . . ." After I went back out I heard a loud bang a few minutes later.

"When I came into the hall I saw the defendant come out of the processing room holding a revolver. He had both hands on the gun and be fired it four times.

"I turned to the officer on my right (Swart) and said, 'Let's get the hell out of here . . .' A minute later I saw he had blood on his short and he was holding his chest. There was blood coming out of his month. He staggered forward a few steps and fell over."

A few minutes later when Johnson was captured by other officers he and Melvin were placed in Roberts' custody. Under cross-examination, Roberts said he had stripped both naked.

Asked by Mundy hy he had stripped them, Roberts his voice shaking slightly, answered, "because when a guy shoots at me and I have custody of him, I'm going to search him good, I'll go as far as taking his clothes off. Anybody can kill you, not just someone who's big."

At one point when Mundy was questioning Roberts about the size of Johnson Brothers Roberts said he had no idea how big Melvin was. "Here I am," Melvin said, jumping up from his second row seat.

"Sit down," Femia barked, ending the only disturbance of the hearing.

When Femia announced his decision, Johnson, dressed in a heavy green striped sweater, never moved. He kept his hands tucked under his chin and stared straight ahead.

He left the courtroom with his family, lawyers and supporters in near silence. His trial is now scheduled to start on Nov. 13 although it seems likely that it will be postponed.