After months of claiming he wanted to confront his Abscam accusers in court, Rep. John M. Murphy (D-N.Y.) rested his bribery trial defense today without taking the witness stand to explain his videotaped conversations with undercover FBI agents.

The announcement by his attorney, Michael Tigar, stunned prosecutor Thomas P. Puccio, the courthouse audience, and attorneys for codefendant Frank Thompson Jr. (D-N.J.). Murphy and Thompson, both influential House committee chairmen, are accused of taking $50,000 payoffs after promising undercover agents that they would help a fictitious Arab sheik with his immigration problems.

Tigar and Murphy refused to answer questions about their decision not to present any defense witnesses. But it was viewed as a sign both that they considered the government case against Murphy weak and that they didn't want to give Puccio a chance to cross-examine him.

Much of the prosecution case has focused on Thompson's role in the alleged conspiracy to take money from the Arab "sheik." But in sharp contrast to the August trial of since-expelled representative Michael (Ozzie) Myers (D-Pa.), Murphy and Thompson flatly deny ever getting the alleged payoff money.

Myers admitted he took it, even returned to ask for more, and was convicted. Attorneys for Murphy and Thompson, on the other hand, have contended throughout this trial that Howard Criden, a Philadelphia lawyer convicted along with Myers, kept the payoff money for himself.

Murphy's decision not to testify was especially notable because he has been the most vocal of the six House members and senator indicted since the Abscam investigation was disclosed last February. At every pretrial court appearance, Murphy held news conferences announcing his intention to testify.

Murphy acknowledged he was taking the offensive as a campaign tactic in his fight for reelection. But both he and Thompson were defeated at the polls this month.

After Tigar's surprise announcement today, U.S. District Court Judge George C. Pratt dismissed the jury for the Thanksgiving holiday. Puccio and the defense attorneys will sum up their cases Monday and the jury is now expected to start deliberating Tuesday.

Most of today's session was taken up with Puccio's continued cross-examination of Thompson. The silver-haired congressman flatly contradicted testimony last week in which Rep. John Murtha (D-Pa.) named him as the key actor in the alleged conspiracy.

Murtha, an unindicted co-conspirator in the case, said that Thompson told him on the House floor a year ago that he could get a share of $50,000 in "walking-around money" by dealing with the Arab businessman.

According to Murtha's testimony, Thompson said that Criden would pick up the money and it would be shared by the three congressmen. "I never said any such thing, Mr. Puccio," Thompson said in a strong, steady voice.

Murtha did meet with the undercover agents last January, but refused to accept money.

Thompson also told Puccio that $100 bills he used shortly after the alleged payoff came from "accumulated savings" which he kept in safes in his Washington and New Jersey congressional offices. In testimony last week, the government showed that Thompson repaid a $3,000 loan in $100 bills and gave a staff member a $1,000 loan, mostly in $100 bills, both within weeks of the alleged payoff.

Criden, who will be tried separately, carried the briefcases containing $50,000 out of a meeting Thompson had with the FBI agents Oct. 9, 1979, in Washington. Criden also handled the money when Murphy met with the FBI men 11 days later in New York. Attorneys for the two congressmen said their clients never knew there was cash in the briefcases.

According to the government's charge, Thompson met Criden Oct. 22, 1979, at a New Jersey motel to accept $25,000 from the transaction with Murphy. Of this, $15,000 was to go to Murphy, with Thompson keeping $10,000.

Thompson told Puccio that he stopped to see Criden for about 12 minutes on his way back to Washington from his Trenton home, though he had already talked to Criden on the phone twice that day. Puccio sarcastically asked what could have been accomplished at this short meeting that couldn't be done by phone.

Thompson said he wanted to tell Criden that he was impatient that promised investments in banks in his district hadn't been carried out.

"Did [Criden] give you an envelope with money in it?" Puccio asked.

"He did not, sir," Thompson replied.