The capital murder trial of a Texas man accused of shooting a sheriff’s deputy resulted in a death sentence this week despite attempts by the defense team to mitigate the circumstances of the murder with a neuropsychiatrist expert witness.  The defense expert presented testimony to the jury that the defendant may have committed the crime involuntarily due to external and internal influences on his brain function, and prosecutors responded by calling to question the expert’s research conducted in preparation for the trial and his objectivity.

Convicted Texas Cop Killer Sentenced to Death

Mark Anthony Gonzalez was convicted earlier this month for the May 28, 2011 fatal shooting of Sheriff’s Sgt. Kenneth Vann at a stoplight.  According to court records, Gonzalez pulled up next to Sgt. Vann and opened fire with an AR-15 assault rifle, hitting the deputy with 26 bullets and killing him.  Gonzalez was arrested after later confessing to the crime, and was convicted for killing Vann after only an hour of deliberations earlier this month.

Jurors debated longer on the matter of appropriate punishment, but ultimately agreed on a death sentence after two days of deliberations earlier this week.  Central to the question about appropriate punishment was Gonzalez’s mental competency at the time of the shooting, and to that point defense attorneys attempted to dissuade a death sentence by calling an expert witness to inform jurors that Gonzalez mental state may have been suspect at the time he opened fire on Sgt. Vann.

Mark Anthony Gonzalez Defense Calls Neuropsychiatry Expert Witness

During the trial of Mark Anthony Gonzalez defense attorneys called a neuropsychiatry expert witness to tell jurors that several internal and external factors could have combined to distort the defendant’s mental state at the time of the shooting.  According to James Merikangas, a neurology and psychiatry expert witness from Washington, D.C., Gonzalez may have suffered a concussion in a fall the week before the shooting, and compounded his problematic mental state by spending the evening before he killed Vann drinking with friends and not eating dinner.

Merikangas told jurors that the combination of a potential pre-existing brain injury and low blood sugar from an evening of drinking could result in a condition known as an “automatism.”  When pressed for further explanation, Merikangas responded, “An automatism is a complex series of actions of which the patient has no knowledge and has no will and it just happens automatically. People with automatisms can drive a car, can carry on conversation and do things without willing it, without wanting to and without knowing about it later when they recover. They have no memory.”

Merikangas did not personally interview Gonzalez and is not a therapist, but his expert testimony was focused on providing a possible explanation for the shooting that diminished the defendant’s intent or malice.  Defense attorneys used Merikangas’s expert opinion in an effort to reduce Gonzalez’s culpability and help him avoid the death penalty.

Prosecutors Challenge Defense Expert Witness in Cop Killer Trial

Prosecutors challenged Merikangas’s expert testimony about Mark Gonzalez’s mental state at the time he killed Sgt. Vann by questioning the defendant’s actions after the crime during which he not only confessed to a friend but also altered the firing pins on his AR-15.  Prosecutors alleged that the defendant demonstrated knowledge of his crime and attempted to cover up his actions, both of which suggest that he was not acting in an automatic state which he could not control.  During cross-examination of the defendant’s expert prosecutors also questioned his objectivity by having Merikangas confess that he is philosophically opposed to the death penalty.

Ultimately Mark Anthony Gonzalez’s neuropsychiatry expert witness was not enough for him to avoid a death sentence.  The severity of the crime, the character of the victim, and the ability of prosecutors to question Merikangas’s expert testimony were enough for the jury to agree on the death penalty.  Gonzalez’s sentence is pending confirmation based on the results of a separate hearing designed to legally settle the defendant’s competency.  Prosecutors are confident that the competency hearing will confirm that Gonzalez comprehends the nature of his crime and therefore uphold his death sentence.