Tanner Horner knew to clean his delivery van. He knew to walk away.

He even lit a cigarette after cleaning that van–not long after the senseless murder of #AthenaStrand before returning his FedEx truck and going home in a new video shown to a jury last week.

He can even be heard telling a family member ‘Love you’ on a call during the drive.

Before that, he tells a supervisor he should get the same truck for his route the next day because he threw up in his and that it smells.

This disturbing and uncaring behavior is now under the microscope in a Tarrant County courtroom before jurors return Wednesday to hear Horner’s attorneys present their arguments as to why the 34-year-old should receive life without parole instead of the death penalty.

Even though the jury wasn’t there to hear it, a lot happened inside the courtroom on Monday.

Both yesterday and today, Judge George Gallagher is evaluating the scope and admissibility of expert testimony from the defense.

He heard from several defense experts who essentially previewed what those jurors might hear about Horner’s mental and neurological history.

One medical expert pointed to childhood lead exposure, extremely low testosterone, prior head trauma, and a history of learning disabilities and mental health issues. He testified that those factors can impact brain development, particularly decision-making and impulse control.

However, he acknowledged he could not directly connect those conditions to the murder.

That’s a big hole for the state to exploit in cross-examination.

Another expert diagnosed Horner with Fetal Alcohol Spectrum Disorder, a condition caused by prenatal alcohol exposure that can impair brain function.

A psychologist testified that Horner is on the autism spectrum, describing him as socially immature with difficulty understanding consequences and expressing emotion.

She also addressed his use of an alter ego called “Zero,” calling it a coping mechanism—not evidence of multiple personalities.

The defense also introduced testimony about Horner’s childhood, including claims he was sexually assaulted at age 9.

Despite those conditions, all experts agreed on one central and pivotal key point:

***Horner is capable of understanding right from wrong.***

Prosecutors challenged the credibility of the expert testimony heard Monday, arguing that some of the conclusions rely on limited or disputed research.