When Judge Robert M. Scott called a sobbing teen-ager "an absolute liar" and lauded a juror as telling the truth, few were surprised at the speed or vehemence of the decision made by the jurist who has been at the center of the Catherine Fuller murder trial.

A determined man who is obssessed with detail, Scott, 64, made it clear from the trial's start five weeks ago that he would be calling the shots in the complex case of 10 young persons charged with beating to death the 48-year-old mother of six. No one -- not prosecutors, defense lawyers, witnesses, marshals, spectators or news reporters and artists -- would be permitted to step out of line.

"Oh, stop that foolishness," Scott snapped yesterday to one defense lawyer who argued it was pointless to continue questioning a witness.

"That is your conclusion, without any substance," Scott told another lawyer, cutting off his motion for a mistrial based on allegations that a juror was aware her daughter knew several of the defendants. Those allegations by a 16-year-old girl led to a dramatic nighttime court hearing Thursday and a series of controversial rulings by Scott that some say may be the center of any eventual appeals.

While his razor-sharp tongue is mostly aimed at the bank of defense attorneys, Scott receives high marks from most of the lawyers for fairness and moving along a trial that posed numerous problems and was expected to take months rather than five weeks to try.

"He may be nasty at times, but he's fair," said one lawyer who has had more than his share of battles with Scott.

The large number of defendants posed numerous difficulties for Scott. However, Scott's major problem was ensuring that each defendant be tried as if he or she had no codefendants.

When a problem arose about overheard statements made by some defendants that implicated others, Scott did not hesitate to order prosecutors to edit out potentially damaging references to other defendants. Scott reasoned that these defendants would not have the opportunity at cross-examination if the defendant who allegedly made the statement did not take the stand.

Yet, Scott was equally firm when he let the government introduce the statement once it had been edited.

After lawyer Robert DeBarardinis complained that a statement allegedly made by his client was so ambiguous that it should not be admitted as evidence, Scott minced no words. "I think it points the finger right at them . . . . " announced Scott before deciding to permit the statement. "You all know what snitching means and so do your clients."

Scott, who has cross-indexed the meticulous notes he has kept throughout the trial, has become something of a memory bank for testimony. When a defense lawyer recently summarized a witness' testimony, Scott interrupted and said he remembered a minor detail differently.

Reaching for the ream of yellow legal pages that he keeps to his right, Scott scanned his notes and announced he was correct. No one was surprised.

Other times, Scott has attempted to advise the lawyers, rephrasing a question or describing out of the jury's presence how he would handle a certain procedure.

"If nobody had mentioned my client you wouldn't hear a peep from me," Scott told lawyer Steven Kiersh when he announced he wanted to cross-examine a government witness who had not placed his client Steven Webb in the Northeast park where the plot to rob Fuller allegedly was hatched.

"Judge, I can try my case," responded Kiersh, who wanted the witness to exclude Webb, whom he knew.

Scott's off-the-cuff remarks have delighted spectators, who often roared with approval when the judge rebuked a lawyer or swiveled in his chair, appearing astonished by a statement. During the trial breaks, audience members animatedly traded "Judge Scott" stories.

When a witness was asked to identify prosecutor Jerry S. Goren, the witness said he was the man "with the curly hair." Without missing a beat, Scott retorted, "You can tell it is not I," the courtroom light reflecting off his large bald spot.

One of Scott's biggest laugh draws of the trial occurred when the defense lawyers made the routine request that charges be dismissed against their clients after the prosecution had wrapped up its case.

"What, your client?" asked Scott, an incredulous look on his face, after lawyer Frederick Sullivan said there was insufficient evidence to continue prosecuting his client, Timothy Catlett. "Do you want me to recite it all? . . . The evidence is replete with his participation in the thing."