According to court records, Rock set his cabin in Fayetteville on fire, then shot his neighbor Brookens and Cutchall as they arrived.
"He's trying to get the court to declare he never should have been tried a second time and should have been released," Nelson said Monday.
In both trials, Rock's attorneys used an insanity defense, but he will act as his own attorney at Thursday's post-conviction relief hearing before Judge Richard J. Walsh.
John Walker, who prosecuted Rock in the first trial, is now the president judge in Franklin County.
Walker and former defense attorney David Rudovsky are among those Rock has requested to testify in the hearing.
Although Rock has sought relief from federal courts in the past, Nelson said this is his first post-conviction relief hearing in a state court. Rock's petition filed with the court last June asks that he be resentenced for third-degree murder, or released.
The petition asserts his attorney in the second trial failed "to file a pretrial motion on double jeopardy grounds based upon the concealment of exculpatory evidence by the Commonwealth during the first trial."
In the first trial, Trooper Randy Kepnure, now deceased, testified he took soil samples from gasoline trails leading away from Rock's home, indicating Rock set the fire from a safe distance, according to Nelson.
Rock's petition stated Kepnure "admitted, at a federal court proceeding in 1982, that he did not take soil samples of the earth from the trails." Rock said evidence that the burn trails were caused by a downed power line was not introduced.
"The Commonwealth used evidence of gasoline trails to rebut the defendant's insanity defense and his claim that he lacked intent," Rock's petition stated.
Nelson noted the Pennsylvania Supreme Court ruled in a 1992 decision that a defendant deliberately denied a fair trial by prosecutorial misconduct could not be retried under the double jeopardy clause.
Nelson said Kepnure's testimony wasn't used in the second trial. He also said the 1992 ruling can't be used for a case tried years before.
Nelson likened it to releasing convicted criminals who hadn't been read their rights prior to the U.S. Supreme Court's Miranda decision.
"Even if you buy everything he's saying ... he has no remedy because the attorney can't be held to the requirement of reading a crystal ball" to determine what courts will rule in the future, Nelson said.