Prince George's County prosecutors thought they had solid cases against both Dion Johnson, 27, and Farad "Rico" Mohammed, 24, charged with murder in a March 1998 drug-related killing.

Prosecutors had a statement that Johnson, the alleged triggerman, gave to police in which he admitted to the shooting. And there were witnesses who had Johnson and Mohammed at the scene of the crime or talking about the slaying.

Johnson was scheduled to stand trial first. And Mohammed's trial was to follow soon after. Prosecutors believed convictions would come quickly and easily. But Mohammed was acquitted by a jury in March. Yesterday, a judge declared a second mistrial in Johnson's case.

And now Johnson faces a psychiatric examination to determine whether he is even competent to stand trial.

The latest mistrial came four days into Johnson's second trial. Circuit Court Judge Theresa A. Nolan agreed with defense attorney David M. Simpson that a prosecution witness's statement to the jury that Mohammed had been acquitted could sway jurors in Johnson's case.

The bizarre denouement to the trial found Johnson bickering with his attorney and siding with the man attempting to put him in prison, Assistant State's Attorney Roland Patterson, that the trial should go forward. Meanwhile, Simpson told the judge that his client did not understand what was happening and should receive a psychiatric evaluation.

As three brawny sheriff's deputies surrounded a visibly agitated Johnson, he told Nolan: "I agree with Mr. Patterson. I prefer to go to trial today."

Johnson added: "I'm the flunky in this thing. I'm the one taking the fall." Cutting off his client, Simpson began quietly talking to Johnson; Nolan announced she was granting a mistrial.

As a deputy snapped handcuffs on Johnson, the defendant said, "This is not right. I want all of the evidence closed!"

"It's becoming a nightmare," Simpson said. "It's a tremendous emotional strain on the family and on Dion. We can't even get to the point where we get a resolution."

In requesting a mistrial, Simpson suggested that Patterson intentionally allowed his witness, James Toth, to blurt out the fact that Mohammed had been acquitted. Patterson strongly denied the accusation to the judge, saying he had warned Toth not to mention the Mohammed trial.

Johnson is charged in the March 5, 1998, slaying of Van Reaves, 41. Prosecutors allege that Johnson shot Reaves, who owed money to Mohammed from a drug deal, at Mohammed's behest.

In January, a jury had been selected, but not sworn in, to try Johnson when Patterson told Simpson that he had just learned police had found the murder weapon. The trial was postponed.

In March, Johnson's trial had barely begun when it was derailed. Moments into his opening statement, Patterson told jurors that Johnson had admitted to police that he did the shooting. Simpson moved for a mistrial, saying Patterson had agreed not to use the statement in the main part of his case. Nolan granted the mistrial.