Justin Silva has been convicted of charges including burglary, kidnapping, and attempted murder against his grandmother during a property dispute at her home near Lemoore.
Silva had been out on bail at the time of the crimes, after being arrested for starting a fire at Fresno's Livingstone's Restaurant just weeks earlier.
He has yet to face those charges.
The Kings County District Attorney's Office says Silva's trial will now enter a sanity phase, where the same jury will decide whether or not he understood the nature and morality of his crimes.
Friends of Silva have said his behavior became erratic after he was diagnosed with a brain tumor in 2016.
Silva faces 30 years to life in prison if convicted and determined to be sane.