Billy Flynn was 16 when he shot Smart with the help of several friends. He pleaded guilty and testified that he was having an affair with Smart's wife, Pamela, and that she allegedly seduced him into killing her husband, the New Hampshire Union Leader said Thursday.
The case was made into the movie "To Die For," staring Nicole Kidman.
Flynn, who was sentenced in 1992 to 28 years in prison, has filed a motion for a sentence reduction that includes testimonials and certificates showing participation in educational programs and involvement with numerous nonprofits and charities.
Gregory Smart's family wants Flynn to stay in prison.
His brother Dean Smart said he wants to write a book about the case from the victim's perspective. "We're looking for someone who's not going to promote Pam's angle or Billy's angle," he told the newspaper. "We're trying to get the victim's perspective across."