Defense attorney Jonathan McDougall said during opening statements in the San Mateo County Superior Court trial of Alexander Youshock that the disorder prevented the disgruntled former student from being able to discern fantasy from reality.
Prosecutors allege that Youshock, now 18, went to the high school on the morning of Aug. 24, 2009, planning to kill his former teacher and terrorize students, and that he prepared by constructing pipe bombs in his room and recording deranged messages in the months before the attack.
Chief Deputy District Attorney Karen Guidotti presented a video that she said Youshock created and left on his bed along with a journal and a suicide note, all three of which investigators found when they searched his home.
The video shows a bearded Youshock wearing a military-style vest and speaking into the camera. His image was superimposed on a backdrop of the American flag, flames and the words "F--- USA" in bright yellow.
"Feel what it's like to be hated by everyone," he said. "Feel what it's like to be me."
Prosecutors allege that Youshock's attack was motivated by his self-imposed isolation and by the hatred he harbored for a Hillsdale High chemistry teacher who had flunked him, and that he gained inspiration from school massacres at Virginia Tech and Columbine High School.
Guidotti read a journal entry from April 2009 in which Youshock wrote about naming his chainsaw after the fatal high school shooting in Colorado.
"I named her Collie. It's short for Columbine ... I love Collie."
Giudotti said that Youshock lied to his mother and told her he was constructing a rocket in order to convince her to buy ingredients to make explosives online, including sulfur, charcoal and potassium nitrate.
Youshock attached 10 of the homemade bombs to a tactical jacket and wore it on the morning he went to the Hillsdale High campus, carrying his chainsaw in a guitar case and wearing a facemask to protect himself from blood spatters, Guidotti said.
Youshock tried and failed to start the chainsaw outside his chemistry teacher's classroom, alerting a security guard and other teachers to the attack.
Prosecutors said Youshock detonated two pipe bombs in an attempt to escape, allegedly throwing one at an advancing security guard and tossing the other down a school hallway as students and staff poured out of classrooms to escape.
He was eventually tackled and subdued outside the building by a teacher, the principal and responding San Mateo police officers.
The defense maintained this morning that Youshock has been diagnosed with schizophrenia, which McDougall said causes Youshock to hallucinate and hear voices and prevents him from being able to tell the difference between legitimate situations and those invented by his paranoia.
McDougall quoted an e-mail sent by the principal of Hillsdale High to Youshock's mother in which he described her son as "increasingly sullen" and "one of the most withdrawn and emotionless students" he had ever known.
The defense said that in the months leading up to the attack, Youshock refused to eat anything but cheeseburgers he cooked for himself, that he took two-hour showers and that he insisted all the lights be left on in the San Mateo apartment he shared with his mother and sister.
McDougall said his client suffers "from a mental disease he did not choose," and that because of the disease, Youshock can't form specific intent and premeditate, as the prosecution has alleged.
Youshock is charged with two counts of attempted murder, two counts of exploding a destructive device with the intent to commit murder, one count of possession of a destructive device in a public place, one count of use of explosives in an act of terrorism, and two counts of possession of a deadly weapon.
He faces life in prison if convicted.