THOUSAND OAKS : Jury Told Killer Does Not Have Disorder


A Superior Court jury was told Tuesday that convicted killer Mark Scott Thornton does not suffer from attention-deficit disorder, a condition that renders people unable to concentrate on tasks for extended lengths of time.

The statement by Linda Calvin, an administrator in the Conejo Valley Unified School District, contradicted weeks of testimony presented by defense attorneys in Thornton’s death-penalty trial.

The 20-year-old Thornton was convicted in December of murdering Westlake nurse Kellie O’Sullivan, who was kidnaped in Thousand Oaks and shot three times at a remote area of the Santa Monica Mountains.


A jury is in the midst of the penalty phase of Thornton’s trial that will decide if he serves life in prison or is put to death.

Under cross-examination, Calvin also acknowledged that Thornton appears to have a learning disorder.

After weeks of sympathetic testimony from defense witnesses, prosecutors are portraying Thornton as a disgruntled bully who was not interested in school. Deputy Dist. Atty. Peter D. Kossoris noted that Thornton has average intelligence and was given many chances to succeed in school.

But defense attorneys are trying to convince the jury that Thornton is the victim of a cruel upbringing and suffers from attention-deficit disorder or other learning disabilities that contributed to his dropping out of high school.

Deputy Public Defender Susan Olson cited 14 separate school reports that suggested Thornton had difficulty learning.

The penalty phase of the trial continues this morning.