Two forensic scientists have added their names to the list of people who don't believe Sirhan Sirhan acted alone when he shot Democratic presidential candidate Robert F. Kennedy in 1968.
Kennedy was gunned down on June 5, 1968, at the Ambassador Hotel in Los Angeles. A gunman identified as Sirhan Sirhan was wrestled to the ground and later convicted as the man solely responsible for Kennedy's murder.
But doubts lingered and conspiracy theories took root that perhaps others were involved in Kennedy's death.
In their new book, "An Open and Shut Case," Robert Joling and Philip Van Praag say that after analyzing audio recordings of the assassination they concluded that at least 13 shots were fired. But the handgun Sirhan used only had the capacity to fire eight shots.
The critical piece of evidence, they say, is an audiotape recorded by a journalist who was traveling with Kennedy.
They also believe that the bullet that likely killed Kennedy entered from the back of his head and pierced his brain. Sirhan is believed to have fired his weapon as he faced the candidate.
"It can be established conclusively that Sirhan did not shoot Senator Kennedy. And in fact not only did he not do it, he could not have done it," Joling said.
Joling and Van Praag's findings support the conclusion of experts who contributed to a Discovery Channel investigation in June. They claimed that the shots heard on the audiotape came from two guns.
But other forensic scientists dismiss these theories, saying the analysis is flat-out wrong.
Van Praag and Joling are talking to forensic experts around the country and lobbying for the case to be re-opened.
"What we would basically like to see at this point, is a new investigation certainly based on new facts that we have come up with, take a fresh look at this case and to bring the authorities in," Van Praag said.
The question is whether, after nearly 40 years, authorities will have any interest in reopening a painful chapter in American history.
Sirhan, now in his 60's, is serving a life sentence in California's Corcoran State Prison. In recent years, Sirhan has claimed he was hypnotized at the time of the shooting. He has been denied parole 13 times.