THOUSAND OAKS : Witness: Thornton Treated Too Late

Convicted murderer Mark Scott Thornton was first diagnosed with a learning disability after flunking kindergarten, but school authorities did not seek mental-health counseling for him until 12 years later, an educational specialist testified Tuesday.

Testifying at the Thousand Oaks man’s death-penalty trial, Carol Horwich Luber said the failure to provide counseling cost Thornton a shot at regaining his mental health.

She also suggested the treatment could have halted a “downward spiral” in his life that ended in the murder of Westlake nurse Kellie O’Sullivan.

A Superior Court jury is hearing evidence to determine whether Thornton, 20, should be put to death for kidnaping and fatally shooting the nurse on Sept. 14, 1993. The jury found Thornton guilty of first-degree murder in December and has the option of sentencing him to life in prison without parole.

Prosecutors on Tuesday suggested that Thornton knew the difference between right and wrong, even without early treatment for his emotional difficulties.

If mental-health treatment would have been provided, “do you know whether he would he have committed murder or not?” Deputy Dist. Atty. Peter D. Kossoris asked Luber.

Superior Court Judge Charles R. McGrath sustained a defense objection to the question and Luber did not answer.

After flunking kindergarten in 1980, Thornton spent the next 12 years in special-education classes either full or part time, Luber testified.

Thornton’s family moved from Los Angeles to Thousand Oaks in March, 1992. Eight months later, officials at Conejo Valley High School finally recommended mental-health counseling for him after he alluded to suicide, testified Luber, a defense witness who was paid about $1,500 to review Thornton’s school history and testify.

“Somebody finally recognized he was having a lot of emotional troubles, and that he needed to be looked at,” said Luber, who did not disclose the results of the mental-health evaluation.