A spokeswoman for the California Department of Corrections and Rehabilitation said she cannot comment on the specifics of Sirhan's case, but parole board hearings generally "are not to decide guilt or innocence."
"The board accepts as fact the guilty verdict," said Terry Thornton. "The purpose is to determine if or when an inmate can return to society."
Pepper successfully won a 1999 civil case against the city of Memphis, in which he argued Memphis police were involved in the assassination of Martin Luther King Jr., for which James Earl Ray, the only suspect was convicted in 1969.
Pepper said Sirhan had been examined by Daniel Brown, a psychologist on the faculty of Harvard Medical School, who found he was "easily hypnotized" and was not faking his inability to remember the crime.
Brown was travelling and could not be reached by ABCNews.com for comment.
"[Sirhan] has whole blocks in his mind that are missing," Pepper said. "He doesn't remember anything,
Sirhan might not remember what took place in the kitchen of L.A.'s Ambassador Hotel on June 14, 1968, but history has not forgotten.
Kennedy, then a U.S. senator from New York, was making his way through the hotel's kitchen soon after winning the Democratic primary. Sirhan entered the kitchen, fired on Kennedy and was soon subdued as bodyguards smashed his hand against a steam table. Sirhan continued to fire, emptying all the bullets in his pistol from his immobilized hand as bullets ricocheted around the kitchen.
Rosey Grier, a former NFL player who had joined Kennedy's security team, entered the kitchen just after the shots were fired and helped subdue Sirhan.
Grier told ABC News.com that he didn't know for sure if Sirhan acted alone. But, he said: "All I know is that he was the man who had the gun. I took the gun out of his hand. He was that man. Evidence wise, I believe police did their job in finding out where the bullet came from."
Grier said Sirhan had "a right to do what he has to get justice," but would not comment on whether he believed Sirhan had been hypnotized, or was worthy of parole.