An admitted drug courier, testifying as the chief prosecution witness at a drug-related murder trial, told a Montgomery County jury yesterday that he witnessed the killing and fled in panic but returned the same night to dispose of the body.

Earl Donald (Jackie) Wallace, 25, a native of Montego Bay, Jamaica, told the Circuit Court jury that the slaying of George Lewis took place in Wallace's Silver Spring apartment and that he saw the defendant, Donovan George Brown of Jamaica, shoot Lewis in the head.

As Brown listened impassively, Wallace said Brown was a drug dealer who accused Lewis of stealing Brown's marijuana and killed him out of revenge.

Wallace said Brown and Wayne Findley, identified in testimony as another dealer, found Lewis at Wallace's apartment on Oct. 3, 1984, and began pistol-whipping him. According to Wallace's testimony, Findley had been using an unloaded automatic pistol to beat Lewis, but Brown reloaded it and was striking Lewis with the barrel end.

"Then I heard a shot, and I was the first one to run out of the apartment," said Wallace. "I was shaking . . . . I knew I was going to be in trouble."

That night, Wallace testified, he drove to Baltimore and hired two "hustlers" to help him remove the corpse for the price of 10 pounds of marijuana. Wallace said he and one of the men put trash bags on their hands, rolled Lewis in a rug and drove to a road that looked "lonely" off Rte. 29 to dump the body. It was found the next day by construction workers.

In three hours of testimony, Wallace described a band of Jamaican-born drug smugglers who made regular trips to Miami and New York, who roomed and "worked" the drugs together, but remained on a first-name-only basis.

Wallace told the jury that he began working a year ago as a courier for a Langley Park drug dealer he knew as "Tom."

Wallace said he, "Tom" and another associate used his apartment in The Point near the White Oak Shopping Center for drug sales and that it was one of four "safe houses" they maintained for purposes of drug dealing in Prince George's and Montgomery counties.

Wallace's testimony was full of nicknames. Wallace knew the defendant as "Prentis," for instance, and another associate as "Pele."

"You just don't ask people's last names," Wallace said at one point. "Most people use aliases."

"Everybody you know uses aliases?" asked defense attorney Paul DeWolfe.

"Most people that I know," Wallace repeated.