A California panel has denied parole for Robert F. Kennedy's assassin Sirhan Sirhan, saying the 78-year-old prisoner still lacks insight into what caused him to shoot the senator and presidential candidate in 1968.

Sirhan's lawyer Angela Berry disputed that, saying Sirhan has shown that awareness, and his psychiatrists have said for decades that he is unlikely to reoffend or be a danger to society.

Two years ago, a different California parole board had agreed with Berry, voting to release Sirhan, but Governor Gavin Newson rejected the decision in 2022.

Berry said she believes the new board members on Wednesday were influenced by Newsom and by the lawyers representing Kennedy's widow and some of his children - several relatives of the slain politician are opposed to Sirhan's release, though not all are.

In rejecting Sirhan's freedom last year, the governor said the prisoner remains a threat to the public and hasn't taken responsibility for a crime that changed American history.

"I do feel the board bent to the political whim of the governor," Berry said after the hearing at a federal prison in San Diego County.

The parole board hearing comes nearly six months after Berry asked a Los Angeles County judge to reverse Newsom's denial. The case is ongoing, and Berry said it was unclear how Wednesday's denial by the board will affect it.

"They found him suitable for release last time and nothing has changed," Berry said.

"He's continued to show great behaviour."

In a three-and-a-half minute message played during a news conference held by Berry in September, Sirhan said he feels remorse every day for his actions. It was the first time Sirhan's voice had been heard publicly since a televised parole hearing in 2011, before California barred audio or visual recordings of such proceedings.

"To transform this weight into something positive, I have dedicated my life to self-improvement, the mentoring of others in prison on how to live a peaceful life that revolves around nonviolence," he said.

"By doing this, I ensure that no other person is victimised by my actions again and hopefully make an impact on others to follow."

Sirhan shot Kennedy on June 5, 1968 moments after the US senator from New York claimed victory in California's pivotal Democratic presidential primary. He wounded five others during the shooting at the Ambassador Hotel in Los Angeles.

Sirhan was originally sentenced to death, but the sentence was commuted to life when the California Supreme Court briefly outlawed capital punishment in 1972.

He was denied parole 15 times until 2021, when the board recommended his release.

Sirhan's 17th parole hearing is slated to be held in three years.