Lawyers for Lyn Nofziger rested their case in the former White House aide's conflict-of-interest trial yesterday without calling Nofziger to the witness stand.

Cheerful and apparently optimistic about the outcome, Nofziger, 63, had been prepared to testify, but his lawyers said they decided against it over the weekend.

"The government simply didn't present any evidence that would necessitate his being called," said E. Lawrence Barcella, one of Nofziger's attorneys. Concern that the prosecution might have turned the occasion to its own advantage, Barcella indicated, was a secondary consideration.

Closing arguments are expected this morning as the trial enters its fourth week. Nofziger was indicted on four counts of illegal lobbying under the Ethics in Government Act, twice for the Wedtech Corp. and twice for other clients, shortly after leaving the Reagan White House in 1982. His new partner in a Washington consulting firm, Mark Bragg, was charged with one count of aiding and abetting.

The trial represents the first major test of the law prohibiting former high-ranking officials from lobbying their old agencies for a year after leaving on any "particular matter" that is of "direct and substantial interest" to the agency.

Much of yesterday's session was spent in spirited argument, after the jurors had been excused, over whether the causes Nofziger and Bragg had been paid to promote were weighty enough to have caught more than passing White House attention.

Renewing requests for directed verdicts of acquittal, Nofziger lawyer Robert Plotkin maintained that the evidence backing up the first count -- based on an April 8, 1982, note Nofziger wrote then-presidential counselor Edwin Meese III on behalf of Wedtech -- was "so sparse, so meager, so sporadic . . .so uncoordinated that there is no way . . .it could amount to 'direct and substantial interest' by the White House."

U.S. District Court Judge Thomas A. Flannery had ruled that such interest must have existed as of the date of the alleged offense. Independent counsel James C. McKay argued that there was "an abundance" of evidence showing White House interest in Wedtech's getting a long-sought defense contract, beginning with a 1980 campaign promise to revitalize the South Bronx where the company was located.

McKay, however, ran into sharp questioning from the judge when he tried to emphasize the role of Detroit businessman Pier Talenti, a $1-a-year volunteer on Nofziger's staff who visited the Wedtech plant in August 1981. According to the testimony of former Wedtech executive Mario Moreno, Talenti said Nofziger had put him "in charge" of getting an Army engine contract for Wedtech "and that the administration and Mr. Nofziger were very interested" in seeing that the award was made.

Pressed by Flannery to explain why he didn't call Talenti as a witness if he was so important, McKay said he would have been antagonistic to the government's case and "we felt we had enough adverse witnesses, Your Honor."

Many of the prosecution's witneses were longtime friends of Nofziger and, as he once observed during a break, it was plain that "they don't want to hurt me."

Plotkin said Talenti would have testified that he had gone to New York at his own expense to see the musical "Evita," that he visited Wedtech only because he had some spare time, and that he did not make the statements Moreno said he did.

Flannery denied all defense motions for acquittal, but he also said he would instruct the jury "to disregard what Mr. Moreno said Mr. Talenti told him."

The other counts involve:

A hotly disputed May 28, 1982, letter to White House aide James Jenkins that Nofziger allegedly signed on Wedtech's behalf.

An Aug. 20, 1982, note Nofziger sent Jenkins as a lobbyist for the Marine Engineers Beneficial Association (AFL-CIO) about expanding the use of civilian crews aboard noncombatant U.S. naval ships.

A Sept. 24, 1982, meeting Nofziger had with National Security Council staffers about continued production of Fairchild Republic's A10 antitank aircraft.