Despite being feared and isolated by the other inmates, a doctor said Horner seemed completely unresponsive and unable to understand why he was being treated this way. A terrifying psychological breakdown

The expert said Horner’s mother had to explain the impact of his actions to help him understand

Credit : Juan Figueroa/The Dallas Morning News via Getty; Wise County Sheriff’s Department

A speech-language pathologist testified that Tanner Horner did not understand why other inmates viewed him as a “monster” after he killed 7-year-old Athena Strand.

“An important example is when Mr. Horner’s mother called him, and he couldn’t understand why his fellow inmates were looking at him like a monster,” the expert, Dr. Amy Fritz, told jurors, according to NBC DFW. “And his mother, knowing his difficulties in this area, had to directly put it in terms he could understand, and so therefore gave him that perspective.”

Fritz said the interaction illustrated Horner’s difficulty with empathy, describing how his mother had to help him understand the impact of his actions.

Juan Figueroa/The Dallas Morning News via Getty

Fritz also testified about video and audio shown to jurors from the day of Athena’s abduction, saying Horner’s behavior did not initially reflect the kind of emotional dysregulation she often sees in people with autism, a diagnosis Horner has previously been reported to have.

“I think that he doesn’t demonstrate the emotional dysregulation that I typically see in individuals on the autism spectrum in the moments prior to and right at the time of the abduction,” Fritz said, according to NBC DFW. “In other words, his language was kind, cautious, easy, and not scary at first, and then became highly disrespectful and horrific towards Athena.”

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Fritz also testified that Horner told her he had backed into Athena and later strangled her, a version of events she said was similar to what he told investigators. She said he did not mention sexually assaulting the child, according to NBC DFW.

Horner pleaded guilty to capital murder and aggravated kidnapping on April 7, PEOPLE previously reported. Jurors are now deciding whether to sentence him to death or life in prison without parole.

Athena disappeared from her family’s Wise County driveway on Nov. 30, 2022, while Horner was delivering a package to the home, PEOPLE previously reported. Prosecutors say he abducted her and killed her inside his truck; jurors have since been shown video and audio from inside the vehicle capturing her abduction and what happened inside the truck.

Her body was later found in a rural creek two days after she vanished, and the medical examiner determined she died from blunt force trauma, smothering strangulation.