Attorneys for a man accused of repeatedly shooting a Houston-area sheriff's deputy at a gas station say a medical expert has deemed him unfit to stand trial.

In a court motion filed Monday, Shannon Miles' attorneys say he has been diagnosed with schizophrenia, that he can't "consult with his attorneys with a reasonable degree of rational understanding," and that he doesn't understand the legal proceedings against him.

Miles, 31, is charged with capital murder in the Aug. 28 killing of Deputy Darren Goforth. Prosecutors say Goforth was filling his squad car at a suburban Houston gas station when Miles attacked him, shooting him 15 times. They allege that he attacked the deputy because he was a law enforcement officer.

In the motion, Anthony Osso, one of Miles' two attorneys, indicated that "his attempts to communicate with (Miles) in a rational manner have proven to no avail."

Miles' attorneys said a report by a psychiatric expert for the defense "concludes with a reasonable degree of medical probability that the defendant is presently incompetent to stand trial."

Jeff McShan, a spokesman for the Harris County District Attorney's Office, declined to comment.

Records show that Miles was committed to mental health facilities twice in the last five years.

Miles was treated at the Harris County Psychiatric Center in 2010, Osso has said.

Miles also spent several months at a state mental hospital after a 2012 arrest at an Austin homeless shelter for aggravated assault with a deadly weapon. Miles was later declared competent but the charge was dropped after the victim couldn't be located.

No trial date has been set. Prosecutors have not decided if they will seek the death penalty. The next court hearing in the case is set for Jan. 13.

Miles remains at the Harris County jail. He is being held without bond.

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