THOUSAND OAKS : Jury Told Thornton Has Brain Disorder

Convicted murderer Mark Scott Thornton suffers from “cerebral disorganization”--a brain disorder that a defense expert said helps explain Thornton’s penchant for violence, a Superior Court jury was told Thursday.

Defense attorneys claim that Thornton shot and killed Westlake nurse Kellie O’Sullivan partly because he suffers from brain damage that causes him to act on impulse.

Testifying at Thornton’s death-penalty trial, Dr. William Goldie classified the defendant as an abnormally slow thinker, based on the results of a brain scan.

Thornton’s brain functions are slower than 95% of the general public, said Goldie, director of neurophysiology at Ventura County Medical Center.

The doctor reviewed the results of an electroencephalograph conducted on Thornton and tested the defendant in reading and math. The doctor also said he reviewed Thornton’s birth, pediatric and school records.

The jury, which found Thornton guilty of first-degree murder in December, must determine whether the defendant should be put to death for killing the 33-year-old nurse. The jury also has the option of sentencing him to life in prison without parole. O’Sullivan was shot in the Santa Monica Mountains on Sept. 14, 1993, after being kidnaped in Thousand Oaks.

Despite the extent of his problems, Thornton’s medical condition could be modified with treatment, Goldie said.

“It does not justify murder, it does not justify anything,” he said outside court of his diagnosis. “It gives us a physiological basis for explaining certain things.”

The 4-week-old penalty trial, in recess until next week, is expected to last another month.