A Prince George's Circuit Court judge upheld yesterday the conviction and 25-year prison sentence of Terrence G. Johnson, who was found guilty in 1979 of voluntary manslaughter in the shooting death of one Prince George's County police officer and found innocent in the death of another.

Johnson had asked Judge G.R. Hovey Johnson in October to overturn the conviction because the trial judge had not told his defense lawyers about a conversation the judge had with a juror. The juror said in the conversation that the jury foreman had told her the black jurors "were sticking together."

Johnson's attorneys found out about the conversation a year after the conviction, when a national law organization surveyed the jurors.

Johnson's attorneys argued that Circuit Judge Jacob Levin, who presided over the trial, had, in effect, denied Johnson his rights to a fair and impartial jury and to challenge a juror. Keith Fisher, one of Johnson's attorneys, said that had Johnson's trial attorneys known about the conversation, they might have asked for a mistrial or to have the jury foreman removed from the panel.

Judge Johnson, in a six-page opinion, said that Levin's failure to tell defense attorneys about his conversation with the juror did not deny Johnson effective assistance of counsel because the conversation did not come at a "critical stage" of the trial.

"The judge assured the juror that there was no cause for concern and asked [the juror] to notify him if she had any further problems," Judge Johnson said. "The judge was not contacted again."

Johnson, who is black, was charged in June 1978 with the slayings of white officers Albert M. Claggett IV and James Brian Swart. Johnson, who was then 15 years old, and his brother had been picked up as suspects in a burglary. The two officers were shot in the county police station in Hyattsville.

Johnson's attorneys first asked Prince George's Circuit Court Judge Howard Chasanow to overturn Johnson's conviction last February because they had not been informed about the conversation between Levin and the juror. Chasanow denied the request. His ruling was upheld by the Maryland Court of Special Appeals.

But a federal court sent the case back to the state courts, saying that Chasanow's ruling didn't address all of the issues argued by the defense.