HOUSTON -- The brother of a man accused of killing a Houston police officer took the stand on Thursday to try and convince jurors that his brother suffers from a brain injury, 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, according to his attorney.

Quintero's older brother was called to testify Thursday afternoon. Jurors were shown a videotape of Quintero's childhood home in Mexico where he supposedly fell 9 feet off a roof as a child.

The brother said Quintero was 6 or 7 years old at the time and was hospitalized for a day or two. He said that Quintero had unusual behavior as a child, such as frequently staring into space and being extremely afraid in harmless situations.

Johnson's widow testified in the morning. She told jurors about her devastation when she learned about her husband's killing,

Houston police Sgt. Joslyn Johnson cried when she was asked where she was when her husband was killed. She answered that she had just gotten off of her shift and was at her son's football game when she got the phone call she never wanted to receive.

Joslyn Johnson told the jury she met her future husband at the police academy in 1994.

She told jurors about her seven-year marriage and the last time she saw her husband when she gave him a good-bye kiss.

She cried when she saw her husband's picture in court.

A medical examiner also testified, showing jurors graphic evidence of Johnson's seven gunshot wounds inflicted from less than 2 feet away.

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 four times in the head 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's attorney said the brain injury left Quintero paranoid and unable to accurately assess situations, causing him to overreact.

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.