Now 33, Tankleff was 17 when he was accused of killing Seymour and Arlene Tankleff in their Belle Terre, Long Island home. Tankleff's relatives, who have always believed in his innocence, hope that this hearing will finally set him free.
Correspondent Erin Moriarty speaks to several key witnesses and reports for "Prime Suspect," Saturday, March 12, at 10 p.m. ET/PT.
Tankleff's private investigator, former New York City detective Jay Salpeter, is working the case pro bono. Salpeter tracked down Glenn Harris, a career criminal who says he harbored a secret for 14 years.
In a sworn affidavit, Harris says he drove two men, Joe Creedon and Peter Kent, to what he thought would be a home burglary in an upscale Long Island neighborhood. Harris says he waited in the car as they entered the house.
When he heard about the Tankleff murders the next day, Harris says, he put "two and two together." At Tankleff's hearing, both Creedon and Kent took the stand to deny any involvement in the murders. But, Harris surprises Marty and his family by refusing to testify on the grounds he might incriminate himself.
As the hearing continues, Harris' priest testifies, with Harris' permission, that Harris told him the same story he told 48 Hours. Other witnesses testify that Creedon had tried to involve them in his plot to murder Seymour Tankleff and others say that Creedon had bragged about being involved in the Tankleff murders.
What's more, Salpeter says, Creedon had been associated with the son of a man the Tankleff family was involved with the crime. That man, Jerry Steuerman, was deeply in debt to Seymour Tankleff. Both Steuerman and his son deny any involvement in the murders.
Assistant District Attorney Leonard Lato is fighting to uphold Tankleff's conviction and says that many of the new witnesses have no credibility because they are criminals. Salpeter says that it makes sense that people willing to work with Creedon would have criminal records.
Tankleff, who has spent his entire adult life behind bars, lived his childhood in the lap of luxury. The key evidence against him was a confession that Tankleff says he was tricked into giving hours after he found his mother dead and his father clinging to life.
Richard Ofshe, an expert in interrogation tactics, explains how innocent people can be persuaded to confess to crimes they did not commit. He tells 48 Hours that Marty's "confession is actually evidence of his innocence" because so many details do not correspond to the crime.