Defense attorneys for Terrence G. Johnson, the 15-year-old youth accused of killing two Prince George's County police officers, yesterday changed his innocent plea in one of the shootings to innocdnt by reason of temporary insanity, bringing an early close to the opening day of his trial.

Judge Jacob S. Levin ordered the trial continued until March 19 and remanded Johnson to the Clifton T. Perkins Hospital for psychiatric examination after the new plea was announced by chief defense attorney R. Kenneth Mundy.

While 300 prospective jurors waited in another courtroom, Mundy told Levin that his client would plead that he was temporarily insane when he shot officer James Brian Swart last June 26.

Mundy had previously told Levin that Johnson would plead innocent by reason of self-defense in the shootings of both Swart and officer Albert M. Claggett in the Hyattsville police station. The self-defense plea in the Claggett case will stand, Munday said.

Munday said he was amending the plea based on examinations of Johnson by two psychiatrists.

What we are saying is that what happened to Terrence in that room with Officer Claggett which led to the first shooting [of Claggett] was so shocking, so traumatic and so overwhelming that he lost control of himself so much that he cannot recognize the criminality of the act, [of shooting Swart] Mundy said. "Technically this is called a transient situational disturbance -- in lay terms, temporary insanity."

The development in the case apparently surprised Levin, as well as the 200 people waiting in the hall to try to get into the courtroom, a small band of demonstrators outside the courthouse and State's Attorney Arthur A. Marshall Jr.

After hearing the new plea -- which he could have disallowed because it was not filed earlier -- Levin retired to his chambers to interview one of the psychiatrists, Frances Welsing.

During the one-hour recess, Helen Johnson, the accused's mother, sat between her daughter and another son, reading the Bible.

When Levin returned to the bench he announced the continuance, saying he thought the state had the right to administer its own psychiatric examination.

Marshall asked that Johnson's $100,000 bond be revoked and that Johnson be sent to Perkins as an inpatient.

"The easiest thing for me would be to revoke bond," Levin said. "But if I did that it might be construed as retaliation for the defense's using every defense available. I have no intention of revoking his bond." But Levin did order inpatient treatment for Johnson, for an examination that will require one to two weeks.

Johnson was placed in the custody of the sheriff's department, although he was not handcuffed. As deputies moved forward to take him from the court-room, Johnson buried his head in his arms and sobbed quietly.

His mother clutched her daughter's arm, tears welling in her eyes.