(NewsNation) — Scott Peterson‘s casual demeanor after learning his pregnant wife’s body had been found revealed his guilt in her 2002 murder, according to the former detective who worked the case.

Jon Buehler, a retired detective who investigated Laci Peterson’s disappearance, said Friday on NewsNation’s “Dan Abrams Live” that what convinced him of Scott Peterson’s involvement was how he reacted after being told DNA confirmed his wife and unborn son were dead.

“Just several minutes later, making his order at In-N-Out Burger for something to eat. The fact that he could just so cavalierly ask for a Double-Double with cheese and a small fry and a vanilla shake after he’d just been given this horrendous news convinced me that he was involved in it because who does that?” Buehler said.

Defense attorney Lara Yeretsian maintained Peterson’s demeanor doesn’t prove guilt, saying people react differently to trauma, and there was no forensic evidence linking him to the crime.

She contended new evidence points to a burglary crew being responsible.

But Buehler dismissed that theory, saying the burglars were thoroughly investigated, and no connections to Laci Peterson were found.

A California judge ordered new DNA testing on a piece of duct tape but denied most other retesting requests.

Peterson, 51, is seeking to prove his innocence 20 years after he was convicted of killing his wife and unborn son, Connor.

The formerly high-profile case that once captivated the nation took another twist as the Los Angeles Innocence Project pushed for modern DNA analysis on several pieces of evidence from the 2002 crime scene.

The next hearing in this case will be held July 1.