A DNA expert said Brian Laundrie "had weeks" to alter, conceal or destroy evidence at the van or the crime scene if he killed his fiancee, Gabby Petito.

Police said Laundrie had returned to his parents' home in North Port, Florida on September 1, with their van but without Petito. 

According to The Sun, authorities did not seize the Ford Transit van until September 11, when Petito's family reported her missing. Laundrie was named a person of interest by the North Port police after Petito was reported missing.

Paul Belli, a member of the International Homicide Investigations Association, told The Sun that Laundrie "had weeks to handle or do things to disturb scenes such as the van."

Belli believed that authorities would have to carry out a lot of "forensic processing" on the van the couple had used to travel. He feared that investigators might not fully know what happened in Petito's final moments.

Belli noted that authorities would need to get a lot of information to have a precise idea of what actually occurred. However, he said there's a "good possibility that they may never know every detail."

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Gabby Petito's Autopsy Results

The investigation over Gabby Petito's death is still ongoing, weeks after coroners in Teton County, Wyoming concluded that she died due to manual strangulation.

An autopsy was performed on her remains after her body was found at the Spread Creek Dispersed Campground near Grand Teton National Park in Wyoming on September 19.

Teton County coroner Brent Blue earlier said that Petito was strangled to death by "human force," and the manner of death was homicide. The cause of death was officially listed as "manual strangulation/throttling."

Blue earlier told CNN that throttling means that "someone was strangled by human force" and "no mechanical force" was involved. He noted that people could be strangled by other means, like individuals on snowmobiles who run into a wire. 

"That would be strangling by a mechanical event. But this was, we believe was strangling by a human being," he said.

When asked how they knew it was a human responsible for Petito's killing, Blue said, "because only humans have opposable thumbs." He added that there was no evidence it was "done by any animal as far as the cause of death."

According to Blue, they conducted a "detailed investigation" in coordination with the FBI that included a full-body computed tomography scan and examinations by a forensic pathologist and a forensic anthropologist.

He also said that Petito was not pregnant at the time of her death, and her body was left in the wilderness for three to four weeks.

The coroner has declined to answer if he suspects that Laundrie was responsible for his fiancee's death, saying it will be up to law enforcement to determine that.

Brian Laundrie's Death

The month-long manhunt for Brian Laundrie finally came to an end after the FBI announced that the skeletal remains discovered in a Florida park belonged to Gabby Petito's fiance.

The remains found at the Myakkahatchee Creek Environmental Park on October 20 were confirmed to be Laundrie after a "comparison to known dental records."

Laundrie family attorney, Steven Bertolino, said the initial autopsy of Laundrie's remains did not uncover a cause or manner of his death.

He noted that the autopsy by the Sarasota County medical examiner did not produce concrete results on Laundrie's death. He said the remains of Petito's fiance were already sent to a forensic anthropologist for further examination.

According to Bertolino, the results of the forensic anthropologist's examination of Laundrie's remains are expected this month.

He said the forensic anthropologist's examination would conclude in two to three weeks. Forensic anthropologists analyze human remains, conduct DNA tests and look for signs of weapon evidence to help determine how a person died, whether accidental, suicide, homicide, or natural.

Gabby Petito disappeared on a cross-country road trip Brian Laundrie. The couple was traveling to Oregon when the YouTuber stopped communicating with her family in Wyoming in late August.

READ MORE: Brian Laundrie Manhunt: Parents of Gabby Petito's Fiancé Change the Date of Florida Fugitive's Disappearance

This article is owned by Latin Post.

Written by: Mary Webber

WATCH: Attorney: Brian Laundrie's Parents at Site Where Remains Were Found - From FOX 13 Tampa Bay