In an apparently unprecendented ruling, a D.C. Superior Court judge ordered yesterday that the jury in a murder case that ended in a mistrial last week must still consider the evidence and render a verdict.

Judge Eugene N. Hamilton then suspended his own order until 10:30 this morning to give federal prosecutors a chance to ask the D.C. Court of Appeals to rule against him. Unless the appellate court rules against him by that time, Hamilton said, he will conclude the trial and direct the jury to begin its deliberations.

The mistrial was ordered last Thursday by Judge Nicholas S. Nunzio on the ground that attorneys for two of the three defendants had failed to conduct themselves effectively. At that point, the trial was midway through final closing arguments to the jury.

The jury was dismissed when the mistrial was declared. On Friday, Judge Hamilton, to whom the case had been assigned when Nunzi recused himself, took the unusual step of calling the jury back and asking each member if he or she could still render an impartial verdict. All said they could. He also reappointed the two defense counsel whom Nunzio had fired for what Nunzio said was their ineffectiveness.

Yesterday's hearings was to determine if the mistrial ruling could be set aside and whether the case could go forward to a verdict. Both prosecutors and defense attorneys argued that going forward was impossible. Both said thejury had been "tainted" by conbersations its members had had and by news accounts they had read between the time the mistrial was declared Thursday and the time Hamilton ordered them back Friday.

Underlying yesterday's arguments was the question of placing the defendants in "double jeopardy" - being tried twice for the same offense.

If Nunzio was correct in declaring a mistrial on the basis of ineffective assistance of defense counsel, then the "double jeopardy" clause of the U.S. Constitution would not apply. This is because of U.S. Supreme Court rulings that defendants are entitled to effective counsel. Prosecutors argued that Nunzio was correct and contended that a new trial should be ordered.

Defense attorneys argued that Nunzio's ruling was unjustified. Since the "jeopardy" of a defendant in a criminal case begins when the jury is sworn in and not when the verdict is rendered, they said that even the recall of the old jury constituted "double jeopardy." They said this also would be true in any future trial.

Judge Hamilton avoided passing on the merits of Nunzio's ruling. He said that as a practical matter he felt that the jury could render an impartial verdict. He indicated that he believed that this would skirt the "double jeopardy" issue.