Former investigator says key evidence wasn't properly investigated in Scott Peterson case

MODESTO, Calif. -- A former investigator says key evidence in the Scott Peterson case may not have been properly examined.

This comes after the Los Angeles Innocence Project recently took on the decades-old case that gripped the nation.

Peterson is currently serving a life sentence for the murders of his pregnant wife Laci Peterson and their unborn child.

Now, nearly 20 years after Peterson was convicted, a former California fire investigator is coming forward to ABC News, urging prosecutors to re-examine the case.

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"This has always been one of those things that kind of sits in the back of your head and kind of bugs you a little bit. You kind of wonder why this didn't happen, or why it wasn't brought up," Bryan Spitulski, a former fire investigator with Modesto Fire Department, told ABC News in an exclusive interview.

Spitulski is speaking out on the heels of a stunning court motion about the potential of new evidence.

Lawyers for the nonprofit now fighting for Peterson are focusing on stains from a mattress in the back of a burned van that tested presumptive positive for blood.

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Spitulski investigated that van in December 2002, which was found the day after Laci disappeared and was less than a mile from the couple's home.

"You know, I don't know that I was tying the moment to Laci. I was more tying the moment that it was human blood," Spitulski said. "It made it like this was much more important than just a burned vehicle that somebody was just wanting to get rid of or cover up a simple crime."

In a court filing, lawyers say DNA testing done on a small portion of that mattress several years later "was insufficient to determine whether DNA from Laci" or their unborn son "was present"

Now, as a private fire investigator, Spitulski says no one from the prosecution or the defense came to him for his evaluation of the van.

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"I don't have an agenda or an opinion on his guilt or his innocence. This is for me -- it's a fire investigation in a vehicle that has blood, possible blood, you know, on the mattress, and that right there is important," he said.

The LA Innocence Project believes enhanced DNA testing could provide more information. However, the district attorney's office says Peterson's conviction was upheld in 2022.