Joshua Gilbreath trial: Defense is building 'insanity defense' in shooting

FLORENCE, Texas - The murder trial of Joshua Gilbreath continued on Monday in Williamson County. His murder trial shifted from a question of reasonable doubt to his state of mind.

Gilbreath is accused of killing Diana Pier in 2022. She was found shot on a rural roadway near Florence. Investigators believe she had stopped to check on Gilbreath, who had pulled over in a driveway. 

Prosecutors have established Gilbreath was angry at the time about losing his job, and Gilbreath’s gun was also linked to the murder, which is why Williamson County District Attorney Shawn Dick said he remains confident in their strategy.

"We believe in our case, we believe it’s a murder case, and we believe in the jury system," said Dick.

Gilbreath’s attorneys are trying to show his behavior changed shortly before the murder and intensified when he was fired from his job.

Prosecutors spent Monday countering that argument. Key testimony came from Gilbreath’s former roommate, Ryan Sutton. He testified that Gilbreath was known for not taking anything seriously, and for making random comments just to antagonize people. 

Sutton went on to say Gilbreth abused cocaine, although his use tapered off just before the murder. Sutton, when questioned by the defense, did admit he initially told investigators that Gilbreath was acting schizophrenic. Prosecutors tried to convince the jury strange behavior is not proof of insanity.

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"It's really more about soft science, and its people’s interpretation of whether this person could appreciate the wrongfulness of his conduct due to some mental health issue that they have," said Dick.

Despite that, winning an insanity plea in a Texas courtroom is still difficult for defense attorneys.

"And their burden of proof is by the preponderance of the evidence, so it’s more likely than not that Mr. Gilbreath committed this act while insane," said Dick.

On Monday, a mental health expert, Christine Reed, testified. 

Reed told the jury when she examined Gilbreath, he admitted shooting a woman and claimed she made a motion like she was going for a gun. Reed testified it’s her opinion that intoxication and substance abuse were significant factors in his behavior.

Gilbreth also indicated he knew he did something wrong and, according to Reed, that undermines an insanity plea.