Austin Harrouff, right, who is accused of killing a Tequesta couple in 2016, listens as his attorney Robert Watson addresses Martin County Circuit Judge Sherwood Bauer, Jr. (not pictured) during a hearing Thursday, June 13, 2019, at the Martin County Courthouse in Stuart, Fla. (Leah Voss/TCPalm.com via AP)

Attorneys for a Florida man accused of killing a couple and chewing the husband's face attacked the constitutionality of the state's laws governing insanity defenses, arguing it wrongly places the burden of proof on defendants instead of prosecutors.

Austin Harrouff, 22, has said he was fleeing a demon-like figure when he ran to a home and attacked the couple living there, spitting out a piece of flesh when deputies arrived and were finally able to subdue him.

An attorney for Harrouff told Circuit Judge Sherwood Bauer Jr. the law's requirement that defendants prove insanity to a “clear and convincing” level of proof discriminates against the mentally ill because it is a higher burden than for defendants who claim self-defense or duress. Under self-defense, the burden is on prosecutors — they must prove it wasn't. Defendants who claim duress must only prove that it is more likely than not that they acted out of necessity.

Attorney Robert J. Watson said it is also unconstitutional that jurors are told before deliberations they are to presume the defendant is sane. He argued that goes against Harrouff's right to be presumed innocent of the August 2016 killings of John Stevens and Michelle Mischcon Stevens. Bauer questioned Watson extensively on this point, asking him how this is unfair to Harrouff.

Watson replied that to convict Harrouff of first-degree murder, prosecutors must prove beyond a reasonable doubt he killed the Stevenses with evil intent. He said since Harrouff is not disputing he killed the Stevenses, his only defense is that his mental illness made it impossible for him to form intent. Given that, Watson said, it is unfair that jurors are told to start with the presumption that “the defense is invalid” unless proved otherwise.

“We are not presuming you are insane, which is what we should be doing if we are applying a presumption of innocence,” Watson argued.

Prosecutor Jeffrey Hendriks said there is no discrimination in Florida's insanity law against people with mental illnesses. He said some states don't even allow an insanity defense.

Bauer said he would rule soon. Harrouff's trial is scheduled for the fall.

Harrouff told the “Dr. Phil” television show two months after the attack that he was fleeing a demon he called “Daniel” when he ran to the Stevenses' home. About 45 minutes before the attack, he had stormed out of a restaurant 2 miles away, where he had argued with his father. Earlier, his mother had found him at her home drinking cooking oil mixed with Parmesan cheese; a lawsuit filed by Michelle Stevens' family alleges the concoction was spiked with hallucinogenic mushrooms. Harrouff told host Phil McGraw that he doesn't clearly remember the attack.

According to court documents, deputies arrived to a horrific scene at the Stevenses' home. Michelle Stevens, 53, lay mangled and dead in the garage and Harrouff, then a muscular exercise science major at Florida State University, was attacking and biting her 59-year-old husband in the driveway. Harrouff is alleged to have also wounded a neighbor who tried to save the couple.

One deputy ordered Harrouff off at gunpoint while another used an electric stun gun on him, but he wouldn't let go. Deputies say they didn't shoot Harrouff because they feared hitting John Stevens.

Finally, a deputy with a dog arrived and its bites enabled deputies to subdue Harrouff, who had no previous arrest record. He told deputies, “Help me, I ate something bad” and then admitted it was “humans” as he spit out a piece of flesh, court documents show. He begged deputies to kill him after they pulled him off Stevens, according to the records.

“Shoot me now; I deserve to die,” Harrouff said.

He had to be hospitalized for two months as he ingested an unknown chemical from the Stevens' garage, burning his esophagus.

If convicted, Harrouff faces life in prison without parole. His attorneys want him committed to a mental hospital for life.

Terry Spencer reports for the Associated Press.