HOUSTON -- The trial of a man accused of killing a Houston police officer entered its second week Monday, KPRC Local 2 reported.

Officer Rodney Johnson was shot in his patrol car on Sept. 21, 2006, after a traffic stop in southeast Houston.

Juan Leonardo Quintero, 33, has been charged with capital murder of a police officer. He has pleaded not guilty by reason of insanity because a childhood injury left him with brain damage that made him paranoid and unable to accurately assess situations, according to his attorney.

Quintero's mother, sister and second-grade teacher were in the courtroom for the first time to lend their support.

His former teacher testified about Quintero's lack of ability to concentrate in class.

A large group of Houston police officers has been in the courtroom throughout the entire trial to support Johnson and his widow, who is also a Houston police officer.

"Rodney and I were close friends throughout our whole careers," Lt. Randy Upton said. "I believe it's appropriate to come show my support to his wife, Joslyn, and their family and let them know that even in Rodney's passing, we have never forgotten him."

A psychologist took the stand on Monday. He told the court that he examined Quintero twice. The judge was expected to rule on whether or not he could be used as an expert witness for the defense. The judge ruled that a neuropsychologist would be allowed as a defense witness. In a pretrial hearing, the neuropsychologist said Quintero's brain scans showed signs of brain damage.

Quintero told police in a videotaped statement that he killed Rodney Johnson because he was being given a ticket for driving without a license after he was stopped on suspicion of speeding.

Police said Quintero shot Rodney Johnson after Quintero was put in the back of a patrol car during a traffic stop in southeast Houston. Investigators said Quintero used a 9 mm handgun he had hidden in his waistband.

Quintero is a Mexican citizen who was deported in 1999 after being convicted of indecency with a child, but sneaked back into the country, according to authorities.

Before the trial began, Quintero offered to plead guilty in exchange for a sentence of life in prison, but prosecutors rejected the offer because they are seeking the death penalty.