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Defendant in 2018 stabbing case can discuss his mental health at trial

A room inside the Idaho Supreme Court with multiple empty chairs and two flags.
James Dawson
Boise State Public Radio

Ruben Diaz, who allegedly stabbed and slashed an elderly man’s face in 2018, will be allowed to argue in court he didn’t know he had attacked a human.

Prosecutors sought to block an expert witness from testifying on Diaz’s behalf.

A report from a licensed psychologist retained by Diaz found he suffers from paranoid schizophrenia and that he believed he attacked an alien – not a human – that day.

The Idaho Supreme Court Wednesday unanimously sided with a lower court ruling to allow Diaz to use the expert’s testimony in defending against an aggravated battery charge.

“…the State cannot show that he intended a forceful or violent contact against another person if they cannot show he knew the subject of his attack is human,” justices wrote in the opinion.

Idaho is one of four states in the country that doesn’t allow an insanity defense. These states, however, do allow for what’s called a mens rea defense – meaning you can’t be convicted of a crime that you don’t know you’re committing.

Justices touched on that in their ruling, saying “evidence of mental condition is still expressly permitted to rebut the State’s evidence offered to prove criminal intent.”

Idaho’s aggravated battery law doesn’t explicitly require Diaz knew he was injuring another human, but the court said: “that knowledge is implied from the statute and must be proven to sustain a conviction for the same.”

An investigation by the Idaho Statesman found Diaz had been diagnosed with schizophrenia and autism sometime before 2008. It also found he would stop taking his medication and threaten violence or attack people who he thought were aliens.

A spokesman for the Idaho Attorney General declined to comment on the ruling.

Diaz’s trial was originally set for March of 2020, but it has not been rescheduled.

Follow James Dawson on Twitter @RadioDawson for more local news.

Copyright 2022 Boise State Public Radio

I cover politics and a bit of everything else for Boise State Public Radio. Outside of public meetings, you can find me fly fishing, making cool things out of leather or watching the Seattle Mariners' latest rebuilding season. If you have a tip, please get in touch!

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