Abuse a child and, while the body matures, emotional development is "stunted."

That's the situation in which Cody Posey was forced to cope, a psychologist testified Friday on behalf of the boy.

Witnesses have testified they saw the father's and mother's physical, verbal and emotional abuse of Posey over many years.

Psychologist Dr. Susan Cave examined Posey in October 2004. She testified she recognized the classic post-trauma symptoms of nightmares, flashbacks, intrusive thoughts and "a phenomenon called disassociation where a person detaches and is apart from himself." A layman, she said, would call it "spacing out."

Cave said the abuse and Posey's trauma met head on in a deadly collision in the summer of July 2004. Not only did she say it was a tough time for Posey, at his age it was also the most strenuous time in any youth's life.

"I think that most parents would agree that junior high school is the most difficult time," she said, pointing out it's when hormones bring about body changes, and children begin seeking peer approval as well as outside interests.

"It's a big transition," she said.

Regardless, according to Cave, children do not begin thinking cognitively -- as an adult comprehends and reasons -- until age 16. But she said when a child is abused, emotional development is stunted at the point the abuse occurred. Witnesses have testified Posey was beaten as early as 2-1/2 years old.

What Cave termed the "precipitating circumstance" that led Posey to kill was his narration of a sexual assault. On July 4, the night before the shootings, he said his father attempted to force his son into sex with Tryone. When Posey said he repeatedly refused, his father burned him on the arm with a hot wire. Defense lawyer Gary Mitchell has entered into evidence photographs of those burns.

Psychologically, the attempted rape "overwhelmed (Posey's) self control" and created an "up welling of fear, anger, feeling like he just couldn't tolerate (abuse) anymore," Cave said.

Following the scene in his parents' bedroom, Posey has testified he went to a corner of his room and curled into a fetal position. He had been wounded emotionally, Cave said, and feared the next attack.

"We can't forget that he was 14 years old," Cave said. "That was a child who was looking for some kind of safety. ... I think with his history, with the very recent attempted sexual assault, the burning by his father, I think that he was overwhelmed by emotions at the time and felt that he was in imminent danger -- which doesn't necessarily mean it's going to happen in the next 60 seconds but that it could happen any time."

Cave diagnosed Posey with several mental illnesses. She said he was hyper-vigilant or "always on the alert" for the next assault. At the same time he exhibited the classic demeanor of "over control": keeping a lid on emotions and putting "on a blank face because it's not safe to laugh or cry."

He suffered major depression, as well as chronic low-level depression "dating back to early childhood when his mother first ... abandoned him,'" she said. Fueling depression was losing his first stepmother, Sandy, who has testified she often rescued the boy from his father's punishments.

Cave also diagnosed him with post-traumatic stress disorder.

"Given that he saw his mother die literally in front of him, that's enough of a precipitating stressor to lead to post-traumatic stress disorder which you see in his bad dreams, sense of abandonment, recurring thoughts about it, flashbacks, etc.," Cave said.

Posey was 10 when he was in the vehicle accident in which his mother was killed.

Posey also suffered adjustment disorder, which Cave described as reacting to stressors. One symptom is misconduct.

On cross examination, Senior Trial Prosecutor Sandra Grisham queried Cave as to the validity of the diagnoses, if Posey was lying.

"Would it affect your opinion?" Grisham asked.

"Possibly," Cave said.

As Grisham has repeatedly emphasized, she believes Posey was not out of control because of what she has characterized as the calculating way he prepared for the shootings, carried them out, then hid the bodies and attempted to destroy evidence.

"All the covering up he did showed his intent to get away with it, didn't it?" Grisham asked.

"It showed some poor judgment, some adolescent thinking," Cave said.

"In fact many of his actions that morning show the ability to show intent," Grisham said.

"Yes, it could be interpreted that way," Cave said. "I'm not saying he was out of touch with reality."

"Doctor, you cannot testify to a reasonable degree of psychological certainty that Cody Posey lost control of his actions," Grisham said.

"I think I can," said Cave. "I think his ability to reason was diminished due to the circumstances, and he lost control of himself."

"That wasn't my question," Grisham said, and asked that question again, then a third time when she didn't feel she got a proper response.

"I think if he had any other avenue (of exit) available to him he might have taken it," Cave said.

A frustrated Grisham started to ask a fourth time when Mitchell objected, stating Cave had responded to the best of her ability.

"You got all the answer you're going to get," Judge James Waylon Counts told her.

The defense's final witness was a former ranch hand on Sam Donaldson's ranch in the summer of 2003. He's now a Marine at Camp Pendleton, Calif. Private Steven Chavez's deposition was read into the record.

Chavez spoke of numerous times he witnessed abuse. He recalled "very, very bad" language and insults toward Posey by his father and stepmother. He described Delbert Posey dropping a rock onto the boy's back; and squeezing one of Posey's fingers "really hard" with pliers and threatening to rip his fingers off. It hurt Posey so badly, Chavez said, marks were impressed into the flesh and caused the boy to cry.

Senior Trial Prosecutor Janice Schryer has called the abuse allegations nothing more than "character assassination of people not alive to defend themselves."

Following Mitchell resting, Grisham wasted no time in beginning her rebuttal. She has 39 witnesses scheduled.

"How long do you expect the rebuttal case (to last)?" Counts asked.

"A week," Grisham said.

Asked why the large number, Grisham told the Daily News, "That's because we're trying a different case than he (Mitchell) is."