A former Prince George's County Police informant testified today that he recruited two men at police request to hold up a High's Dairy store in Adelphi where waiting officers shot and killed one of the men and arrested the other in 1967.

Gregory Gibson, 33, told a federal court jury here that Police Det. Joseph D. Vasco Jr., now the second-highest-ranking official in the county police department, made most of the arrangements for the staged robbery on June 8, 1967, including selecting the store, providing Gibson a getaway car and showing him an escape route.

In exchange for his cooperation, Gibson said, Vasco promised to help eliminate criminal charges pending against Gibson in the county.

Members of the police stakeout team at the High's robbery and a series of others in 1967 became known as the "death squad" in police circles.

Gibson and other witnesses in the current $9 million wrongful-death civil lawsuit against three members of the squad and two county officials accused of authorizing their actions have been ordered by presiding Judge Herbert F. Murray not to use the term "death squad" in testimony before the six-member jury.

The lawsuit was brought by survivors of two men shot and killed by police in the series of 1967 robberies and two men arrested in the incidents.

Several points in Gibson's dramatic step-by-step description of the High's holdup varied from those of another witness against alleged "death-squad" members, retired police officer John R. Cicala, and attorneys representing police accused of staging the holdups have challenged much of Gibson's account as spurious.

Gibson, for example, testified that only one shot was fired during the High's holdup--a shotgun blast from police that killed William Hunter Matthews, 18, one of the two men Gibson had recruited for the holdup.

Cicala testified earlier this week that he heard "shots" inside the store from where he was standing on the roof of the building as part of the stakeout team. Cicala also told investigators three years ago that he heard both heavy shotgun fire and lighter "small-bore" fire from a pistol.

Matthews was armed with a .32-caliber pistol, but Gibson testified today that Matthews did not fire it. He said that after he and Matthews entered the store, Matthews raised the pistol in the direction of a policeman posing as a clerk and was shot immediately by another officer hiding in the rear of the store. He said police gave no warning before shooting.

A third participant in the incident, Marvin Rozier, 18, was arrested unharmed outside the store near the getaway car.

Defense attorneys contend the sequence of events was different. Lawyer James P. Salmon told the jury in his opening statement that Matthews entered the store, pointed the pistol at the clerk's head and cocked the weapon. He said police in the rear of the store then yelled "Halt, police," and when Matthews wheeled toward the rear, both Matthews and police fired "almost simultaneously."

Police fired three times and Matthews once, Salmon said.

In addition, Salmon and other defense attorneys contend Gibson did not recruit robbery participants at Vasco's request, as Gibson has testified, but merely reported to police that a holdup was being planned so that police could stake out the location.

Besides Vasco, the two other alleged members of the "death squad" named in the lawsuit are Capt. James Fitzpatrick, commander of the police department's major crimes division, and retired Lt. Blair Montgomery.

The lawsuit also accuses 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.

The "death-squad" incidents occurred more than 15 years ago but allegations against members of the squad did not come to public light until 1979 in a series of articles in The Washington Post. Claimants against the police subsequently filed the present $9 million lawsuit, contending among other things that police violated due process provisions of the 14th Amendment.