OCD most often is manifested as compulsive hand-washing, cleaning and counting, testified psychologist Linda Gummow.

But Houston's compulsions were violent and sexual in nature, perhaps because of incidents in his childhood, Gummow testified.

Houston saw his father put a knife to his mother's throat, and he was raped by an older male, she noted.

Gummow said she was the first person to diagnose Houston's OCD, which she said is often overlooked in children. She added that Houston's OCD may have been exacerbated by his treatment and supervision at Youth Health Associates, where the boy was placed by juvenile court authorities following two prior sexual assaults.

Supervision was "lax," Gummow said, but Houston is most comfortable in a rigid environment.

Houston was able to skip school, stay home and have sex with a girlfriend without the knowledge of YHA, according to prior testimony.

Gummow said Houston's sexual thoughts could have been hightened by talking to his female YHA therapist about his fantasies, adding medication is the best treatment for OCD.

It did not help that Houston was able to hear his adult supervisor at the home having sex with his girlfriend on occasions when the girlfriend visited and stayed overnight, she said.

"It stimulated the sexual thoughts he was fighting," Gummow said.

Houston, now 18, last month pleaded guilty to capital murder for the Feb. 15, 2006, stabbing death of 22-year-old Raechale Elton.

Because he was 17 at the time of the crime, Houston is not eligible for the death penalty.

A 2nd District Court jury must decide only between the sentences of life with or without the possibility of parole.

Elton was killed after giving Houston a ride home during a snow storm, a violation of YHA rules which prohibit staff members from being alone with clients.

Jurors learned Thursday that Elton had broken rules against fraternization at a prior job, according to a stipulation between prosecutors and the defense that was read in court Thursday.

Elton was fired in June 2005 from a Utah drug court program because she was visiting clients in their homes and inviting clients to her home, according to the stipulation. Despite warnings, Elton continued to break the rules at Frontier Probation.

On the day she was fired, Elton told her boss that she refused to "give up her friend," according to the stipulation.

Elton also told her boss that she "felt she could heal them with friendship."

The case could go to the jury later today.