A former life insurance salesman, convicted of commissioning an Arlington couple's murders in order to collect insurance benefits, was handed a prison sentence yesterday that will keep him behind bars long after the pair's confessed killer is free.

The sentences a Virginia judge imposed on Jospeh N. Martin -- a life term for one murder; 20 years for the other -- were the harshest Martin could have received under a jury's recommendation.

"Some see this . . . as a miscarriage of justice," said Arlington Circuit Court Judge Charles S. Russell, commenting on the disparity between Martin's sentences and one he had imposed earlier on Richard Lee Earman, the couple's admitted killer.

Earman, 37, who was acquitted of, but later confessed to, the killings, received a 10-year prison sentence on a murder conspiracy charge last month. The sentence, the result of a plea bargaining agreement with former prosecutor William S. burroughs, will make Earman eligible for parole in about 2 1/2 years, although a presentencing report recommended that no parole be granted.

Martin, 29, however, will have to serve at least 20 years in Virginia prisons before he can be considered for parole, according to prosecutors.

Despite his admission, Earman could not be tried again for the murders because of the Constitution's protection against double jeopardy. Russell made clear yesterday he was troubled by the unequal sentences.

"Here is a man [Earman] with a terrible record who has been an absolute blight on society -- and he escapes with a 10-year sentence," the judge said. "But it is the genius of our civilization that we think it right to live with that unhappy result."

The judge then looked at Martin, who has grown a beard while awaiting his sentencing day in the Arlington jail. "Two wrongs don't make a right," Russell told Martin in a firm voice and then pronounced his sentences.

Martin was convicted after a six-week trial for murder-for-hire and second-degree murder in the deaths of Alan Foreman, 26, and his 24-year-old fiance Donna Shoemaker on Dec. 13, 1977. Prosecutors argued that Martin, an agent for New York Life Insurance Co., hired Earman to kill Foreman in a complicated scheme to collect on a $56,000 insurance policy that Martin had sold to Foreman.

Martin, according to the prosecution, needed the insurance money to cover premium payments on other fraudulent insurance policies he had created for other people and to maintain what prosecutors termed "a flashy life style, way beyond his income."

Earman, who was to have received $15,000 from Martin for killing Foreman, appeared as a key witness against Martin.

The original murder plot called only for the killing of Foreman, Earman testified. But Earman said when he informed Martin that Shoemaker might have to be killed, too, because the couple was almost always together, Martin agreed.

Defense attorneys Gerard Treanor and Louis Koutoulakos sought to undermine Earman's testimony during the course of the trial, characterizing him as a notorious liar.

These attacks continued yesterday as Koutoulakos asked Russell to give Martin concurrent rather than consecutive sentences.

Earman is "just as competent with the Big Lie as any man that ever lived," Koutoulakos said. "It wouldn't send a dog to jail on the basis of Mr. Earman's evidence."

Special prosecutor, Donald S. Caruthers Jr. argued vigorously against concurrent sentences for Martin, saying that Martin deserved to serve time for Shoemaker's death as well as for Foreman's.

"When two efforts grow out of the same cause, there is an emotional pull to lump it all together," Caruthers said. "But Alan was killed for money. Donna was killed for nothing. Her life would be thrown on the heap."

Russell ruled against the defense motion without comment.

Burroughs was replaced by the special prosecutor because of his role as a witness against Martin and was not in court yesterday. Burroughs, who lost his bid for reelection in November, was criticized for his handling of Earman's 1977 murder trial and the subsequent plea-bargaining arrangement.

Martin's sentencing seems to write a conclusion to the celebrated case, although defense attorneys yesterday attempted to win a delay in the sentencing, saying they have reason to believe that new exculpatory evidence will soon come forward.

Judge Russell struck that note of finality as he surveyed those assembled in his courtroom and said: "I doubt if any of us will again experience anything like it."