Imagine that you're a parent. You have a son with brain damage, who has an IQ of 78. He has repeated epileptic seizures, and can neither work nor drive. He doesn't have enough money to eat, and shoplifts foodstuffs from convenience stores and pizza parlors to eat. He doesn't appear to be at all violent; just mentally disabled, and very troubled.
And then, one day, he comes in and tells you that he took a gun from your house and shot six individuals dead in cold blood -- three in a Quik Stop convenience store and, on another occasion, three more at a Round Table Pizza. The police perform ballistics tests on your gun and discover that it was indeed the weapon used in the killings. Your son is then sentenced to death.
A nightmare, to be sure. For the parents of the victims as well.
Needless to say, the California Supreme Court unanimously affirms the conviction and death sentence.
P.S. - Just one random snippet of the stuff that the defendant did during his trial: "On September 13, 1994, the trial court was considering a defense motion to exclude the media from the hearing on defendant’s motion for change of venue, when this exchange occurred: The Court: "Let’s take a short break. [¶] Defendant has his finger up.” Defendant: “I am guilty.”" Not exactly stuff you want your client to volunteer if you're his defense counsel. Especially since they can (and do) use the statement against him at trial.