Jurors Hear Death Penalty Arguments for Convicted Killer : Courts: Prosecutors cite Mark Scott Thornton’s violent tendencies while defense blames brain damage for his crime.

Mark Scott Thornton is a ruthless killer whose violent tendencies did not begin or end with the death of Westlake nurse Kellie O’Sullivan, a prosecutor charged Monday, imploring a jury to send the convicted murderer to his death.

But in opening statements at Thornton’s death-penalty hearing, his lawyer urged the jurors to spare the defendant’s life.

The defense attorney said Thornton’s life was scarred by a traumatic birth, brain damage and years spent with an unfit mother, all factors contributing to his decision to shoot O’Sullivan and steal her truck.

“Basically, what you need to find is that Mark Thornton is so bad, so terrible that he needs to be exterminated,” said Deputy Public Defender Susan R. Olson, suggesting that the jury give him life in prison instead.

The conflicting portrayals came as the jury in Ventura County’s most high-profile murder case in years began hearing evidence to decide whether the 20-year-old defendant should live or die.

Last month, the same panel in Superior Court convicted Thornton of first-degree murder under a special circumstance that qualifies him for a death sentence.

Thornton, who shot O’Sullivan three times after kidnaping the 33-year-old nurse Sept. 14, 1993, expressed little emotion as he sat at the defense table with his chin resting on his right hand.

Monday marked the first time prosecutors specified why they are seeking the death penalty in the case, a decision that was made more than a year ago.

Deputy Dist. Atty. Michael K. Frawley, in his half-hour address to the jury, cited the brutal conditions under which O’Sullivan died, as well as allegations that Thornton had committed other violent acts before and since the slaying.

Throughout his statements Monday, Frawley kept referring to the victim as “the 33-year-old working mother,” an apparent attempt to capitalize on the fact that O’Sullivan had a 6-year-old son and a steady job.

Eleven months before the murder, Thornton kidnaped and sexually assaulted a former girlfriend, the prosecutor said. And three times since being jailed for O’Sullivan’s slaying, guards have discovered homemade knives in his cells. The weapons were created from old toothbrushes and razor blades, he said.

*

Frawley also said that Thornton fought with three guards after one search of his cell. “You’re lucky there were three of you . . . because I was looking to stick you,” the defendant allegedly warned one guard.

The defense played down the allegations of jail misconduct and the assault on the former girlfriend. They said those events, even if true, pale in comparison to the conviction for murder.

Olson was careful to repeat that Thornton has no excuse for taking O’Sullivan’s life. But she said a lifetime of physical and emotional abuse, most of it heaped on him by his own family, explained how he wound up becoming a killer at age 19.

“Mark Thornton was not born a 19-year-old with a gun in his hand,” she said.

Speaking for nearly two hours, Olson said Thornton’s life began spinning out of control, ironically, even before he was born. His mother was beaten by his alcoholic father when she was pregnant with him, and that abuse could have led to some brain damage.

Markita Sarrazin also experienced several other serious complications with her pregnancy and Thornton’s eventual birth, she said.

“Mark’s traumatic birth was a fitting start,” Olson said.

Thornton’s father never had any contact with his son and died at age 30 due to a drinking problem, Olson said. The defendant’s mother, a 19-year-old drug addict at the time of her son’s birth, was never fit to raise a child, Olson said.

Many of those child-rearing duties were relegated to Lois Thornton, the defendant’s maternal grandmother. The grandmother is an addicted horse gambler who suffers from depression, Olson said.

Olson pointed out that Thornton’s mother only attended two sessions of her son’s seven-week murder trial.

On the second trip, she was arrested on charges of welfare fraud. Released four days later, the mother never came back to support her son in his fight for his life, Olson said.

The defense attorneys said the mother’s absence from court is significant because it reflects her general indifference to Thornton’s life.

From his conception, Thornton was like “a seed thrown on the ground and no one watered it and cared for it,” said Olson, who has apparently become close to the defendant during the course of the case. She often can be seen handing him tissue and offering him support during particularly intense moments in court.

Olson told the jury that she did not want to “trash” the mother. But she said she was best at teaching her son how to steal, cheat and lie. Markita Sarrazin has always been more interested in pleasing her various boyfriends and husbands, Olson said, than tending to the needs of her brain-damaged son.

Noting that Thornton persistently denied murdering O’Sullivan immediately after his arrest, Olson said: “Where did Mark learn to lie to the police? He learned it at home.”

Olson also referred to allegations that Thornton had beat a former girlfriend.

“Where did he learn to hit?” she said. “He learned it at home.”

As a result of being raised in a deprived environment, Thornton never learned to love or respect himself or anyone else, Olson said.

Olson said medical doctors will testify about the extent of the brain damage. She said Thornton flunked kindergarten and was in special education throughout his years in school. He dropped out of school in the 10th grade, she said.

*

Defense attorneys will call as witnesses family members, including Markita Sarrazin, and a long list of psychologists and educators, Olson said.

“You will hear testimony from two neurologists who will testify that Mark’s brain functions abnormally,” Olson said.

Speaking to the jury first, Frawley said that Thornton has been diagnosed as having average intelligence. Thornton’s former teachers could not determine whether the defendant suffered from a learning disorder “or was simply L-A-Z-Y,” Frawley said, spelling out the word.

He said Thornton’s biggest problems in schools were that he was inattentive, unmotivated and frequently absent. In just one year of high school, Thornton was missing up to 25% of the time, Frawley said.

Frawley said the defense will try to generate sympathy for Thornton. But he said, “Not one defense witness will tell you that Mark Scott Thornton did not know right from wrong.”