Cayley Mandadi, 19, was a sophomore at Trinity University when she was brought to a Texas hospital on Oct. 29, 2017. She was nearly naked, bruised and not breathing. Her sometime boyfriend Mark Howerton told doctors they'd taken ecstasy at a music festival and she passed out after consensual sex in his car. She died at the hospital.

In February 2018, authorities charged Howerton with Mandadi's murder, alleging her cause of death was blunt force trauma to the head. A year later, Howerton's trial ended with a hung jury.

A new trial was set for 2023. Mandadi's mother Alison Steele and stepfather Lawrence Baitland believed for the second trial jurors needed more information about what happened inside Howerton's car. Steele, a scientist, and Baitland, a NASA engineer, launched their own investigation.

"I needed to be able to show the jury what happened to Cayley," Baitland told "48 Hours" correspondent Peter Van Sant.

Using autopsy photos and consulting with experts, they developed a theory.

Would the couple's investigation change the course of the second trial?