The court, in a ruling issued in San Francisco, unanimously rejected an argument by Ahkin Mills, 38, that an error in jury instructions deprived him of a fair trial.
Mills was convicted in Alameda County Superior Court in Oakland in 2009 of first-degree murder of Jason Jackson-Andrade, 27, of Sacramento, on April 21, 2005, and was given the sentence of 50 years to life.
Jackson-Andrade, a kitchen worker at the University of California at Davis, was unarmed and did not know Mills. He was awaiting a train to Sacramento when Mills approached him, asked whether he had a gun, and fired 11 bullets at him, hitting him seven times.
Mills testified at his trial that he thought Jackson-Andrade had a gun. He said he believed he was under a death threat from the leader of a Crips gang in Merced and had recently moved from Merced to Rodeo to escape the alleged threat.
A defense psychologist said Mills suffered from a paranoid delusional disturbance, in which he was hypervigilant and misinterpreted minor or benign situations as grave threats.
Prosecutors argued, however, that Mills was sane and intentional in his actions and may have had a reason such as a gang initiation rite for the shooting.
Mills admitted he killed Jackson-Andrade but had two defense claims. The first, which was rejected by the jury, was that he sincerely, although incorrectly, believed he had to act in self-defense and should be convicted only of a lesser crime of manslaughter.
His second defense, which was presented in a second phase of trial after he was found guilty, was that he was insane at the time he shot Jackson-Andrade. The Alameda County jury rejected that claim as well.
As required by a state law then in effect, Superior Court Judge Larry Goodman told the jurors they should presume that Mills was sane for purposes of the first phase of trial, and await a possible second phase before considering his insanity claim.
Mills argued in his appeal that the instruction on presumed sanity in the first phase was unfair because it undermined his argument that a delusional disorder caused him to believe he was in danger.
In a ruling written by Justice Carol Corrigan, the state high court said the sanity-presumption instruction in the guilt phase of trial was improper and should not be given in such cases in the future.
"An instruction on the presumption of sanity only complicates matters at the guilt phase by injecting the subject of sanity before it is at issue," Corrigan wrote.
But the court said the record of evidence and testimony at the trial showed that the improper instruction did not harm Mills' defense and that his conviction should therefore be upheld.
"His inherently improbable version of the shooting conflicted with the physical evidence and the testimony of many witnesses.
"We are satisfied that a result more favorable to the defense was not reasonably probable absent the instruction on presumption of sanity," Corrigan wrote for the court.
A lawyer for Mills was not immediately available for comment today.