The brutal patchwork of knife wounds to the face and neck of a Santa Rosa man believed to have been slain by his son could point to the personal nature of the killing, a forensic pathologist testified Tuesday.

But Dr. Kelly Arthur-Kenny, who conducted the autopsy on Mark Herczog, 63, couldn't say if they were consistent with the actions of a madman.

She testified in the second day of trial for Houston Herczog, 22, who has pleaded not guilty by reason of insanity to the November 2011 slaying in the family's Rincon Valley home.

Arthur-Kenny testified that she found at least 60 wounds, including 26 to the head alone, and about 10 slices across the front of the neck. One of Mark Herczog's ears dangled from a thread of skin and he had a fractured skull, she said.

Gruesome photographs of the injuries taken during a nine-hour autopsy were shown to jurors. Earlier, evidence technicians displayed several chefs' knives that were thought to have been used, including one that was bent at a 90 degree angle.

Pictures of a blood-smeared guitar amplifier police believe was used to crush Mark Herczog's head were also shown.

"His face was surely targeted," Arthur-Kenny said under questioning from defense lawyer Karen Silver.

As in previous hearings, Houston Herczog, a 2009 Santa Rosa High School graduate, remained hunched over and staring down at the defense table during the testimony. The disheveled man diagnosed by three doctors as having schizophrenia shook slightly throughout the presentation.

Asked by Silver if the neck incisions could have been made by someone trying to cut off the victim's head, Arthur-Kenny responded that it could be perceived that way, although the wounds weren't deep enough.

She said they were likely inflicted toward the end of the attack after Mark Herczog had lost much of his blood.

But Arthur-Kenny said she couldn't address a follow-up question about whether the cuts were consistent with the work of an insane man thinking he was exorcising evil spirits.

Silver has said Houston Herczog thought his father was possessed and was trying to kill him.

"I have no experience in psychology of that sort," Arthur-Kenny said.

The trial will continue Thursday with a videotaped interview of Herczog by detectives. Jurors are expected to begin deliberating as soon as Friday.

If Herczog is convicted of murder, jurors will listen to a second phase of the trial to determine if he was insane at the time. Doctors who examined Herczog are expected to testify.

He would either be sentenced to prison for up to 25 years to life or be treated indefinitely at a state mental hospital.

Family members have urged the later, arguing the killing happened during a psychotic break.

But a psychiatrist for the prosecution countered Herczog acted under a drug-induced psychosis.