Los Angeles (CNN) -- A controversial assertion by convicted Robert F. Kennedy assassin Sirhan Sirhan to win his freedom was challenged this week by the California attorney general who said "overwhelming evidence" exists against Sirhan's claims.
Sirhan's attorneys have said that a second gunman actually assassinated Kennedy in 1968 and that Sirhan was hypno-programmed to fire a gun as a diversion.
"In sum, (Sirhan) cannot possibly show that no reasonable juror would have convicted him if a jury had considered his 'new' evidence and allegations, in light of the overwhelming evidence supporting the convictions and the available evidence thoroughly debunking (Sirhan's) second-shooter and automaton theories," Attorney General Kamala Harris said in federal court papers filed this week.
Sirhan, the sole person convicted of killing Kennedy, is seeking a new trial or freedom from his life sentence based on "formidable evidence" asserting his innocence and "horrendous violations" of his rights, defense attorneys said in federal court papers filed last year.
Harris, who is asking a federal court in Los Angeles to dismiss Sirhan's request, conceded in court papers filed Wednesday that his lawyers may be able to show two guns were involved in Kennedy's assassination. Kennedy was seeking the Democratic presidential nomination when he was killed.
But even if Sirhan's lawyers can show 13 shots were fired in the Kennedy shooting, Sirhan shouldn't be released from prison, Harris said.
"The mere possibility that more than one firearm was discharged during the assassination does not dismantle the prosecution's case" against Sirhan, the attorney general said in the latest court documents.
Harris said Sirhan is relying on acoustic expert Philip Van Praag's analysis of a tape recording of the Kennedy shooting that concludes 13 shots were fired during the murder and "demonstrates the existence of a second shooter because (Sirhan) only fired eight shots."
The attorney general argues that even if there were a second gunman involved in the Kennedy shooting, Sirhan hasn't proven his innocence.
Sirhan "at most has shown that, according to Van Praag, two guns could be heard firing 13 shots in an audiotape of the shooting," Harris said.
Authorities have said eight bullets were fired in the kitchen pantry of the former Ambassador Hotel in Los Angeles, with three bullets hitting Kennedy's body, a fourth passing harmlessly through his suit coat and the rest striking five other victims, who survived. Kennedy, younger brother of the assassinated U.S. President John F. Kennedy, was shot shortly after midnight on June 5, 1968, only moments after the presidential candidate had claimed victory in California's Democratic primary election. He died the next day.
Defense lawyers William F. Pepper and Laurie D. Dusek say Van Praag's analysis of the tape recording shows two guns fired 13 shots -- five more gunshots than Sirhan could have fired from his eight-shot revolver. Sirhan had no opportunity to reload his gun in the pantry.
Harris calls Van Praag's analysis "pure speculation."
The recording of the Kennedy shooting was made by freelance reporter Stanislaw Pruszynski. ABC News television videotape of the hotel ballroom, where the senator had just claimed victory in the California primary, shows Pruszynski holding his recording equipment in his left hand while descending a small set of ballroom steps, approximately 40 feet away from the kitchen pantry shooting, and moving towards the pantry during the period when the shots were being fired there, off-camera.
Harris said that even if it could be proven "that a second gunman successfully shot Senator Kennedy, (Sirhan) would still be guilty of the charged crimes." She said that under California's vicarious liability law, "an aider and abettor 'is guilty not only of the offense he intended to facilitate or encourage, but also of any reasonably foreseeable offense committed by the person he aids and abets'."
The defense argues Sirhan did not knowingly fire at Kennedy but thought he was shooting at circular targets on a firing range. They contend Sirhan was a victim of hypno-programming by conspirators who programmed him to fire shots as a diversion for the senator's real killer.
For his hypo-programming defense, Sirhan is relying on Daniel Brown, an associate clinical professor in psychology at Harvard Medical School who has interviewed Sirhan for 60 hours over a three-year period, according to defense attorneys.
But the attorney general rejected the hypno-programming claim.
"The theory that a person could be hypnotized into planning and committing a murder against his will is a controversial (if not fantastic) one and has not been adopted by most of Brown's peers, including the American Psychological Association," Harris wrote.
"Thus, even if (Sirhan) could show that some psychologists believe in mind control or hypno-programming, his showing of actual innocence is nevertheless based on a debatable theory that is not universally accepted in the psychology community," Harris said.
Sirhan, who turns 68 next month, was denied parole at a hearing last year where he once again claimed to have no memory of the Kennedy shooting, an assertion Sirhan has maintained since 1968.