The testimony should have been excruciating: a son recounting how he helped a friend kill his own father, telling jurors he was responding to voices in his head.

But Michael Fitzgerald spoke slowly, with a flat affect, showing no sign of whatever emotion he may have been feeling inside.

"I started hearing my voices and they started yelling at me, telling me to hurt my dad," Fitzgerald told a Jefferson County jury Thursday. "I grabbed the post-hole digger and threw it like a spear. It hit him in the stomach."

Fitzgerald took the stand to testify against his friend, Michael Tate, who has been charged with first-degree murder in the Nov. 8, 2004, bludgeoning death of Steven Fitzgerald, 41.

Michael Fitzgerald already has pleaded guilty to second-degree murder in connection with the case and is serving a 62-year sentence.

Prosecutors say the two boys, 16 and 17 at the time, had run away from a social services placement and broke into the Fitzgerald home in Westminster to steal a car. They encountered Steven Fitzgerald in the garage.

Michael Fitzgerald told jurors he hid at first behind a car while Tate attacked his father. Steven Fitzgerald tried to defend himself with a scooter but Tate began hitting him with a shovel, the younger Fitzgerald recalled.

After Tate yelled for help, Michael Fitzgerald said, he joined in, throwing a post-hole digger at his father.

"I saw my dad fall to his knees," Fitzgerald said. "I saw Tate hit him in the face and head with the shovel. My dad falls to the ground face first and rolls over, and Tate kept hitting him in the face. Multiple times. Eight or 10 times. I started crying. I started seeing blood come out of his mouth, and he was shaking really violently and then all of a sudden he stopped."

After the murder, Fitzgerald said the pair went upstairs to change clothes. Tate was eating ice cream and "told me to stop crying and acting like a little baby," he said.

After the murder, Fitzgerald said he went to his parents' bedroom and gathered family photos, preparing to flee to Ireland.

The two boys were arrested at a vacant building nearby.

Michael Fitzgerald said Tate had brought up the idea of killing his parents before, when the pair burglarized the home on Nov. 7, 2004. "I told him I didn't want to kill my family because I loved them too much," he said.

Michael Fitzgerald's mother, Kris, sat in the courtroom throughout her son's testimony Thursday. She listened quietly, but visibly tearful, as he told jurors about how his father died.

Although both boys have a history of mental illness, court-appointed doctors found them sane at the time of the killing.

Tate's defense team contends he should be found not guilty by reason of insanity.