Richard Lee Earman told an Arlington jury yesterday he repeatedly lied to police and prosecutors about a 1977 double murder in which he was involved in order to make his story sound more convincing and confuse authorities.

Earman, a 36-year-old former real estate man, was testifying at the Circuit Court trial of Joseph N. Martin, who is accused of hiring Earman to kill Alan Foreman and Donna Shoemaker in order to collect on a life insurance policy.

The couple was found shot to death in the garage of their North Arlington home in May 1977. Earman, acquitted by a jury of a murder charge later that year, since has pleaded guilty to a murder conspiracy charge in the case and testified in court he shot the couple to death. He is awaiting sentencing and could receive up to 10 years in prison.

Earman is key witness at the trial of Martin, 28, a former life insurance salesman, who could be given the death penalty if convicted.

Under cross-examination yesterday by defense attorney Louis D. Koutoulakos, Earman confirmed he had told a reporter he lied to the authorities. "I've been around long enough so I know that if you tell them things they want to hear, they just eat it up," Earman declared.

Koutoulakos asked Earman: "So there's no question that you lie whenever it suits your convenience?" Earman said "yes," but added, "I did kill those people."

Earman said his lies included denial of complicity in the slaying attempts to implicate innocent persons and an assertion that Martin gave him $3,000 in advance of the slayings.