A former police informant testifying against Prince George's County police officers accused of entrapping and killing two men in 1967 told a federal judge here today his life "might be taken" this weekend if he tries to continue testifying next week.

"At this point, I believe that if I have to wait till Monday, my life might be taken," said Gregory Gibson, 33, in slow, measured tones outside the presence of a jury hearing the $9 million civil damage case against the police.

Gibson, visibly perturbed, did not say if he had evidence of any danger.

Attorneys for both sides quickly met with presiding Judge Herbert F. Murray in a bench conference outside the hearing of spectators.

Murray then turned to Gibson and said, "I appreciate your concern . . . but I think your fears will turn out to be unfounded." The judge indicated he expected to see Gibson in court Monday. The trial does not convene on Fridays.

Gibson left the building accompanied by a woman who had been sitting in the spectators' section of the courtroom.

His dramatic statement marked the second time in this trial that a witness has expressed fear of testifying against the accused officers, three members of a so-called "death squad" who allegedly staged a series of holdups in 1967 in which two suspects were shot and killed by police and two others were arrested.

Earlier this week, John R. Cicala, a retired policeman and self-acknowledged member of the "death squad," testified he failed to go before a grand jury in 1967 with allegations of misconduct against his fellow officers because he was "in fear of my life."

Under cross-examination, he acknowledged he had no specific evidence of danger.

The three officers who are defendants on the suit are Joseph D. Vasco Jr., now second highest ranking official in the county police department, Capt. James Fitzpatrick, commander of the major crimes division, and retired Lt. Blair Montgomery.

Survivors of the two men killed in the 1967 holdups, as well as the two men arrested in the incidents, have accused the three of directing informants to recruit participants for holdups at which police were staked out in advance.

They allege in their $9 million wrongful-death suit that Vasco and Montgomery provided informant Gibson with a getaway car and selected the time, date and location of a High's dairy store holdup on June 8, 1967, in Adelphi in which one of Gibson's recruits, William Hunter Matthews, 18, was shot and killed by police and a second recruit, Marvin Rozier, 18, was arrested.

The allegations first came to public light in a series of articles in The Washington Post in February 1979. The plaintiffs in the current trial filed their suit thereafter.

Attorneys for the policemen deny the allegations, contending the store was routinely staked out by officers after Gibson reported to them that a robbery was planned. They say Matthews came armed with a hair-trigger pistol, which he pointed at a policeman posing as a clerk in the store, and was shot when he fired at officers ordering him to halt.

Claimants against the police also accuse Prince George's County State's Attorney Arthur A. Marshall Jr. and former assistant state's attorney Benjamin R. Wolman of authorizing or acquiescing in the "death squad" stakeouts.

Gibson testified today he came to believe that "Bud Marshall and Ben Wolman had nothing to do with what Joe Vasco and I were involved in."

He said Vasco had originally told him he would ask Marshall and Wolman to get pending criminal charges against him dropped in exchange for Gibson's cooperation as an informant. However, Wolman "never gave me the impression he was working with anyone other than doing his job, as assistant state's attorney," Gibson said, and he accused Marshall of railroading him into the state prison system's mental institution, where he was found "intellectually deficient and emotionally unbalanced."

At another point today Gibson testified that a group of police officials, including Vasco, came to his apartment "in the same year as the newspaper articles" and interrogated him about the 1967 High's store incident--an apparent reference to an official county police investigation ordered by County Executive Lawrence Hogan after the Post articles were publshed.

Outside the presence of the jury, Gibson testified: "I lied to them . . . so they'd leave me alone."

When "my home was invaded and I was intimidated," he said, " . . . I told them I've known Joe Vasco a long time, he's one of my best friends and I'd do anything for him."

Indicating that those statements had somehow been included in a Maryland State Police report on the High's incident, Gibson said, "That document is a damn lie."

At that point, Gibson told Judge Murray he feared his life "might be taken" if he continued to testify next week.

Attorneys representing Vasco and other police are expected to cross-examine Gibson next week on the county and State Police investigations of the High's incident.