Thornton Pleaded to Be Adopted, Friend Says : Courts: Defendant, who could receive the death penalty, cries as witness Bertha Siy recounts episodes from high school.

Convicted killer Mark Scott Thornton wept quietly Wednesday as a family friend told a Superior Court jury how the death-penalty defendant pleaded with her to adopt him when he was a high school sophomore.

The display was not the first time Thornton, 20, has cried in court. But it appeared to be his most extensive emotional breakdown in front of the jury deciding whether he should live or die for killing Westlake nurse Kellie O’Sullivan.

Jurors, who found Thornton guilty of first-degree murder in December, looked on intently as both Thornton and witness Bertha Siy sobbed and sniffled and wiped tears from their faces. The jurors showed no emotion.

Also Wednesday, defense attorneys revved up their attack against Thornton’s parents--suggesting his mother and stepfather did not give Thornton love and support because they were too busy taking drugs and partying.

Defense attorneys, who have been presenting evidence in the penalty phase for nearly four weeks, said they will rest their case today.

Prosecutors say they will spend the next two weeks calling witnesses to rebut the lengthy defense case before both sides present closing arguments. The jury is expected to begin deliberating in mid-March, lawyers said.

The defense case has centered around a contention that Thornton was raised by neglectful, abusive parents and that he has a learning disability caused by brain damage from a traumatic birth.

Taken together, these factors help explain why Thornton shot O’Sullivan after kidnaping her in September, 1993, the defense contends.

In 1991, Thornton attended 10th grade in Glendale after Siy and her husband agreed to take him in so he could attend Hoover High School. The woman’s husband, who did not testify, worked with Pierre Sarrazin, Thornton’s stepfather, she said.

Under the arrangement, Thornton lived with the Siys during the week and went home to his own family on the weekends. Thornton’s family lived in Los Angeles until moving to Thousand Oaks in the spring of 1992.

Siy and Thornton cried in court when she recalled how he would often ask her to adopt him. She was uncomfortable with the request, she said, and the defendant moved to Thousand Oaks with his own family in 1992.

In Thousand Oaks, Thornton attended Thousand Oaks High School, where he was diagnosed as severely emotionally disturbed, said Anna Merriman, then a child-welfare coordinator at the school.

To help Thornton, the school assigned him to its most restrictive classroom program, which required him to remain in the same class four periods a day, said Merriman, now an assistant principal. Other students switched classes after each period, she said.

Merriman also testified that Thornton told her that his family was in disarray and that he only felt close to his grandmother, who lived out of the county.

Merriman also told the jury that Thornton told her that his father had died when he was a toddler.

Merriman said that she felt “he had never gone through the grieving process” over his father’s death. Superior Court Judge Charles R. McGrath instructed the jury to ignore the comment, ruling it inadmissible.

Thornton was often truant at school, but was not a major behavioral problem, Merriman said.

He once was assigned to a four-hour detention after hitting another student in the head with a book, she said. The student was not seriously injured and school officials concluded the incident was a result of horseplay, Merriman said.