The judge in the Iran-contra trial of John M. Poindexter yesterday rejected a renewed defense request to conduct a further examination of whether the former national security adviser's prosecution was improperly influenced by his immunized congressional testimony.

U.S. District Judge Harold H. Greene held that a June 1 sealed filing by Poindexter's lawyers had again failed to demonstrate that independent counsel Lawrence E. Walsh had relied on any of Poindexter's immunized testimony.

Walsh was prohibited by law from using evidence derived from Poindexter's July 1987 testimony to the select House and Senate Iran-contra panels.

Greene's ruling reaffirmed his earlier decisions on the issue, including a May 29 opinion in which he rejected a defense request for a post-trial hearing on the possible use of immunized testimony.

Poindexter was convicted April 7 by a U.S. District Court jury on all five felony charges lodged against him, including conspiracy and lying to and obstructing congressional inquiries into the Iran-contra affair.

Poindexter's latest request for a post-trial hearing was based on 38 incidents documented by Walsh's office in which prosecutors reported their exposure to Poindexter's testimony.

"Any instances of exposure were minor, accidental and wholly harmless," Greene said in a memo.

On Monday, Greene is scheduled to sentence Poindexter, who is facing a maximum term of 25 years in prison and $1.25 million in fines.

Richard W. Beckler, Poindexter's chief lawyer, has urged Greene to spare Poindexter a prison sentence, saying the retired Navy rear admiral has already been punished enough.

Poindexter, 53, "has lost a bright and promising career in the United States Navy; he has endured public ridicule of the Congress and the media, and he has suffered financial hardship," Beckler said in court papers filed Thursday.

Poindexter resigned as former president Ronald Reagan's national security adviser in November 1986 when the Iran-contra scandal erupted. He retired from the Navy a year later.

A Navy spokesman said yesterday that Poindexter's retirement pay, which is about $55,000-a-year, will not be affected by his conviction.

Walsh earlier this week asked Greene to imprison Poindexter and said such a penalty was warranted by the nature of the charges, which accuse Poindexter of deceiving Congress.

Beckler noted that none of the six others convicted in the Iran-contra affair has been jailed, and he added that, unlike some of those implicated, it has never been suggested that Poindexter acted "for personal gain or profit."

"Whatever John Poindexter has done," Beckler said, "his actions were always motivated by what he truly believed to be the best interests of the presidency and of the United States."