October 18, 2018 03:59 PM

DNA has been a key dispute in the pretrial phase of Chris Watts‘ prosecution for the alleged murders of his wife and two young daughters. But an expert tells PEOPLE that it is unlikely to prove his guilt or innocence on its own.

Dr. Phil Danielson, a professor at the University of Denver’s Department of Biological Sciences who specializes in DNA collection and analysis, says that while it may hold a pop culture-fueled importance in the minds of outside observers, the reality is much hazier in a homicide case like that of Shan’ann Watts and children Bella and Celeste, her kids with husband Chris.

Within hours of Chris’ arrest late on Aug. 15, authorities announced that Shan’ann had been found in a shallow grave on an oil work site owned by Chris’ former employer (who fired him).

Bella, 4, and Celeste, 3, were found the afternoon of Aug. 16 where they had been concealed for four days in nearby tanks, submerged in oil, according to court filings.

Since 33-year-old Chris was taken into custody, much of the legal maneuvering has centered around DNA: requests for Chris to give up samples of his own, requests to have samples of it collected in a certain way from the necks of his daughters and so on.

Such wrangling has fueled a kind of intertwined speculation by case watchers, based on police statements: One — that Chris must have hidden his kids’ bodies in such a particular manner to destroy the DNA on their bodies; and two — that any possible DNA analysis will prove an inflection point in the prosecution.

Bella (left) and Celeste Watts
Frederick Police

In this view, the DNA on the bodies of Bella and Celeste will either corroborate or debunk the most startling part of the investigation: Chris’ alleged confession to police that he strangled Shan’ann, 34, after watching her strangle Celeste in apparent revenge when he told her he wanted to separate after nearly six years of marriage.

RELATED: After Allegedly Hiding Bodies of Wife & Kids, Chris Watts May Have Left Something Incriminating Behind

According to this confession, as described in an arrest affidavit, he then loaded all three bodies into his truck and stashed them for several days before coming clean to investigators, who had discovered he was allegedly having an affair with a co-worker.

Danielson explains that DNA from Bella and Celeste will not be a decisive factor in confirming what really happened.

“It’s going to be very difficult based on DNA alone to suggest whether or not Mr. Watts strangled his daughters,” he says.

From left: Chris and Shan'ann Watts
Shanann Watts /Facebook

What is certain, he says, is that being submerged in oil only makes DNA retrieval more difficult — but it doesn’t destroy DNA as the two do not mix well.

In fact, in the long term, being buried in the ground is more risky as it exposes DNA to bacteria while oil is “relatively sterile.”

Danielson says the temperature of the oil may be another factor — and it’s unclear how hot the crude was that covered the Watts girls — but oil “in and of itself is not going to guarantee that you’re not going to get any DNA evidence.”

He says that any DNA involved in the case will be trace DNA, also known to the layperson as touch DNA. It can be detected in even minuscule quantities and easily be passed from person to person in ways both direct (via skin to skin contact) or indirect, such as via a surface someone else has touched or between pieces of clothing two people wear when they are washed together, Danielson says.

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“If he [Chris] had been the ex-husband who lived in New England and never saw his daughters and he came out one time to Colorado … and suddenly they’re dead and his DNA is on them, the DNA would be more dispositive or more useful in that kind of case,” Danielson tells PEOPLE.

Still, many years after TV shows such as CSI and Law & Order popularized the notion of clear and convincing forensic work, prosecutors know they need to incorporate DNA into their arguments even if the DNA is not damning by itself, Danielson says.

“[It’s] certainly not going to be the smoking gun,” he says.

Chris Watts
Weld County Sheriff's Office

Danielson says that while at a basic level force and friction will leave more DNA behind — as when someone attacks someone else by hand — that wouldn’t be the only possible explanation if a large sample of Chris’ DNA was conspicuously found around his daughters’ necks (or the reverse: if a lot of Shan’ann’s DNA should turn up in the same place on Bella and Celeste).

One might argue the Watts daughters could have touched a used tissue of their father’s and then touched themselves, Danielson says. Trace DNA moves about so easily, that could explain how evidence of him ended up on them.

But, “DNA being viewed as a very powerful too [by juries],” both sides will “have to address it,” he says.

RELATED: Chris Watts’ Alleged Ex-Lover Speaks — but He’s Not the Co-Worker Police Say Chris Was Seeing

What their dueling experts are likely to differ on is not the science behind DNA analysis but the interpretation of any DNA that is found. Given the different possible explanations, the goal will be advancing an explanation that isn’t just possible but probable.

“The prosecution sees it as necessary to try to use as another nail in the coffin, basically,” Danielson says, “but the DNA by itself is really not all that informative in these kinds of cases.”

Chris has not yet entered a plea to his charges, which include three counts of first-degree murder, and is scheduled to return to court in November. His public defender is forbidden by office policy from commenting on the case.

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