LOS ANGELES (CBS) — Attorneys for Sirhan Sirhan are seeking to overturn his conviction for the 1968 assassination of Sen. Robert F. Kennedy in Los Angeles by arguing that evidence at his trial was faked, according to court papers obtained Monday.

In the most recent appeal filed in federal court in Los Angeles, defense attorneys repeat an earlier claim that a bullet was switched during Sirhan’s trial, proving that he was unfairly convicted of the Kennedy killling.

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Sirhan’s attorneys also suggest that their client had been hypnotized to fire a revolver at Kennedy in the pantry of the Ambassador Hotel in Los Angeles on June 5, 1968, ostensibly to divert attention from the real assassin.

According to the court papers, “expert analysis of recently uncovered evidence shows two guns were fired in the assassination and that Sirhan’s revolver was not the gun that shot Kennedy.”

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Lynda Gledhill, a spokeswoman for the state Attorney General’s office, which is handling the appeal, said prosecutors had no comment.

Sirhan, 67, is serving a life sentence at Pleasant Valley State Prison in Coalinga.

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During his trial, he admitted on the stand to killing Kennedy.