Two jurors in the espionage trial of former FBI agent Richard W. Miller refused to vote to convict him because they believed he had been severely mistreated by his supervisors, another juror said today.

The two holdouts caused a mistrial in a case that has already cost the government "easily in excess of a million dollars," according to an informed source.

Miller, 48, was the first agent of the Federal Bureau of Investigation to be charged with espionage. He faced one count of conspiracy, three of espionage and three of bribery in an alleged scheme to pass classified information to the Soviet Union in return for $65,000 in cash and gold. Earlier this year, two Soviet emigres pled guilty to conspiring with Miller, a 20-year FBI veteran who was fired by the agency the day he was arrested in October 1984.

A mistrial was declared in Miller's three-month-long trial on Wednesday after one juror refused to vote to convict on any of the seven charges and a second juror voted to acquit on the three most serious ones.

The FBI learned that Miller was in a relationship with one of the Soviet emigres, Svetlana Ogorodnikova, more than a month before his arrest and placed him under surveillance.

One juror who voted guilty on all counts said today that the two holdouts "talked as if he [Miller] was set up the whole time . . . . One of them commented they thought he should have been brought in by the FBI when they first found out there was hanky-panky going on, and given him a slap on the wrist, rather than set him up for arrest."

The juror, who asked not to be identified, said the two holdouts were disturbed that much of the government's case was based on statements by Miller during interrogations shortly before his arrest. "They just felt he was under a lot of duress and [was] picked on," this panelist said.

The Associated Press quoted one of the holdout jurors as saying that "Miller was browbeaten and swayed by the interrogation. He would have signed anything put in front of him."

Other jurors identified the two holdouts as Virginia Hennes and Bob Rivera, both of Orange County. Neither could be reached today.

One panelist complained today that the two holdouts had approached the legal issues in the case with emotion rather than logic. "What was so frustrating was they wouldn't listen to the evidence," this juror said. "You couldn't argue evidence with them . . . . In fact, one of them said several times, 'I just have a gut feeling.' Most of the jurors thought the government's case was overwhelming."

U.S. Attorney Robert C. Bonner said today that he will ask for a retrial on all counts.