By Jon Herskovitz

AUSTIN, Texas (Reuters) - The man charged with fatally shooting a Houston-area deputy in a hail of gunfire spent four months in a mental hospital in 2012 after being declared incompetent to stand trial in an aggravated assault case, court documents showed.

Shannon Miles, 30, has been charged with capital murder, a crime punishable by death in Texas. He is accused of emptying a 15-round handgun into Harris County Deputy Darren Goforth on Friday evening as the lawman fueled a patrol car at a Houston-area gas station.

In 2012 when Miles was staying in Austin, he was charged with aggravated assault for allegedly beating up a man at a Salvation Army shelter over a TV remote control, an attack that left the victim with a broken vertebrae, the documents showed.

Miles was declared mentally incompetent and sent to the North Texas State Hospital. He was later deemed mentally competent but the case was eventually dismissed when the victim could not be found.

Miles appeared in court on Monday for an arraignment in the murder case and did not enter a plea.

"A plea of not guilty will be entered," his lawyer Anthony Osso told CNN on Tuesday, adding Miles was being held under protective custody in jail because of the high-profile nature of the case.

It is rare for a jury in Texas to hand out a sentence of not guilty by reason of insanity. The U.S. Supreme Court has ruled that executing the insane is unconstitutional, according to the Death Penalty Information Center.

Deputies found Goforth face down in a pool of blood near his patrol car, dead from multiple gunshot wounds to the back, with 15 .40-caliber shell casings around him, Harris County District Attorney Devon Anderson said in court.

Deputies found a loaded .40-caliber gun in Miles' garage and the same brand of ammunition as the casings found at the gas station, Anderson said. Forensic tests determined the gun was the one fired at the scene, she said.

A witness identified Miles in a lineup as the shooter, Anderson said.

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The slaying came as police handling of minority suspects has become a national issue. Miles is black and Goforth was white.

Harris County Sheriff Ron Hickman said on Saturday the department assumed Goforth was a target because he wore a uniform, and Hickman linked the shooting to the anti-police rhetoric of the "Black Lives Matter" campaign.





(Reporting by Jon Herskovitz; Editing by Bill Trott and Eric Beech)