Los Angeles (CNN) -- Sirhan Sirhan, convicted of the 1968 assassination of presidential candidate Sen. Robert F. Kennedy, should be freed from prison or granted a new trial based on "formidable evidence" asserting his innocence and "horrendous violations" of his rights, defense attorneys said in federal court papers filed this week.

In a U.S. District Court brief, Sirhan's lawyers also say that an 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.

Attorneys William F. Pepper and Laurie D. Dusek also allege that fraud was committed in Sirhan's 1969 trial when the court allowed a substitute bullet to be admitted as evidence for a real bullet removed from Kennedy's neck.

The attorneys further assert that Sirhan was hypno-programmed to be a diversion for the real assassin and allege that Sirhan would be easily blamed for the assassination because he is an Arab. Sirhan, 67, is a Christian Palestinian born in Jerusalem whose parents brought him and his siblings to America in the 1950s....