RIVERHEAD, N.Y. — A prison inmate's claim that he drove the getaway car after a Long Island couple was murdered in 1988 doesn't exonerate the victims' son, prosecutors said Friday.

Martin Tankleff, 32, has been trying to get a new trial since 1990, when he was convicted of the grisly double murder and sentenced to 50 years to life in prison. Tankleff confessed within hours of the Sept. 7, 1988, murders that he bludgeoned his parents and slit their throats.

He quickly recanted and testified later that he was both coerced and tricked by detectives into believing his dying father emerged from a coma and implicated him.

Although divided, various appellate panels upheld the conviction and the methods detectives used to get Tankleff to confess to the murders of retired insurance executive Seymour Tankleff, 62, and his wife Arlene, 53, inside their expansive seaside home in the wealthy village of Belle Terre.

Prosecutors were in court Friday to oppose a defense motion for a hearing on new evidence that two other men killed his parents while Tankleff slept and a third drove a getaway car. The alleged driver, career burglar Glenn Harris, claimed in an affidavit attached to the defense in October that he drove Joseph Creedon and Peter Kent away from the Tankleff home after the killings.

Prosecutor Leonard Lato, who was assigned to look into the new claim because he was new to the Suffolk County District Attorney's Office and had no ties to the trial prosecutor or county police, told Courttv.com that even if Harris is telling the truth it doesn't exonerate Tankleff. Harris would not be in a position to know or prove that Tankleff did not participate his parents' murder, Lato said.

There are also some inconsistencies in Harris' claim.

Defense lawyers say that Harris told their investigator he sat in a car outside the Tankleff home while Creedon and Kent were inside, allegedly to steal from a safe. According to Lato, Harris told a prosecution investigator that he waited at "the bluffs," a cliff overlooking Long Island Sound that is more than a half-mile from the Tankleff home.

Lato said Harris has since hired a lawyer and is demanding immunity before he will talk to prosecutors further. "He's not going to get it," Lato said.

One of Tankleff's appellate lawyers, Bruce Barket, said that Harris' allegation is significant because Creedon's name has come up before and Harris has no motive for lying. Private investigator Jay Salpeter, a retired New York City homicide detective, found Harris in an upstate prison when he began looking up Creedon's past associates.

Even Lato concedes that he found witnesses who said Creedon bragged about killing the Tankleffs in the early '90s. But since a jury found Tankleff guilty of killing his parents, the burden of proving that Tankleff could not have been involved in the murders now rests with the defense, he said.

Barket said the prosecutor is just plain wrong.

"You have to air this stuff at a hearing and see who is reliable and who is not," said Barket, who has until Feb. 4 to reply in writing to the prosecution's motion opposing the hearing.

"If a jury heard all this new evidence, would they be likely to acquit Marty? We say yes, and that's the standard," Barket said. "The standard is not whether I can convict Creedon."

It took Tankleff's jury eight days to find him guilty. Tankleff, who was 17 when his parents were murdered, testified that he woke up, found his father mortally wounded and his mother already dead. Detectives testified that they suspected the high school senior because his demeanor was suspicious and because he wasted no time in trying to implicate his father's business partner.

Tankleff immediately pointed a finger at Jerry Steuerman, his father's business partner.

Jerry Steuerman, the self-styled "Bagel King of Long Island," owed Seymour Tankleff $500,000 and was the last one to leave a high-stakes poker game at the Tankleff home the night of the killings.

A week later, while Seymour Tankleff still lay in a coma and Martin Tankleff was jailed, Steuerman staged his own disappearance by leaving his Lincoln Towne Car running near an airport with front doors wide open. Police found him in a California spa but concluded that he was merely escaping a stressful situation.

Creedon, who was associated with one of Steuerman's sons, has denied any involvement in the murders. Kent also denies any involvement, according to the prosecutor's office.

Tankleff's half-sister has said she believes he is guilty. Seymour Tankleff's brother and Arlene Tankleff's sister, as well as her son, have always insisted that Tankleff loved his parents and is not capable of committing such a crime.

According to the confession jurors heard, Tankleff told police he killed his parents because he was tired of all their rules and because they insisted that he drive "the crummy old Lincoln."