Explainer: Where does the Gabby Petito investigation go now?

The body of Gabby Petito, 22, was found on September 19 in Grant Teton National Park. Photo / AP

Now that the decomposed remains of Brian Laundrie have been found, where does the investigation into the strangling of his girlfriend, Gabby Petito, go from here?

Petito, 22, was discovered slain last month on the edge of Grand Teton National Park in Wyoming, one of the places the young couple had visited during a cross-country van trip that ended with Laundrie mysteriously returning home alone to Florida in the vehicle.

Laundrie, named a "person of interest" in the case, was missing for a month before his skeletal remains were found Wednesday in a swampy wilderness park near his home.

The discovery of the remains come five weeks after Brian Laundrie went for a 'hike' in an alligator-infested Florida swamp. Photo / AP

The case has drawn worldwide interest and numerous theories online from amateur true-crime sleuths. It has also thrown a spotlight on the many missing-persons cases involving women of colour who do not get a fraction of the attention given to Petito, who was white.

Here are some lingering questions:

Can it be proved Laundrie killed Petito?

It could take a DNA match to answer that. Both sets of remains were exposed to the elements and animals for weeks.

The FBI has not said whether there are any witnesses to Petito's killing or its immediate aftermath. One piece of evidence is Laundrie's use of a debit card that didn't belong to him after Petito was listed as missing.

"That would be circumstantial evidence that points to him," said Alfredo Garcia, former dean at the St. Thomas University College of Law in Miami Gardens and a one-time Miami prosecutor. "It's a difficult proposition to establish but not impossible."

The DNA matching effort and any use of fingerprints would be complicated by the fact that the couple were romantically involved and lived together in close quarters. But forensic experts have many techniques to solve crimes despite such obstacles.

"Reconstruction experts can do amazing things, so I would not be surprised if at some point we got a definitive, or near-definitive, conclusion that Laundrie was the killer," said Bob Jarvis, a law professor at Florida's Nova Southeastern University.

Why did the search for Laundrie take so long?

Laundrie, 23, was reported missing from his home in North Port on September 17, two days after he was named a person of interest in Petito's disappearance.

His family said Laundrie left home on September 13, telling parents Chris and Robert Laundrie he was going for a hike in the 25,000-acre (10,100-hectare) Carlton Reserve a few miles away.

Federal, state and local law enforcement officials spent weeks searching the reserve, where at one point 75 per cent of the land had been underwater. The area is home to alligators, bobcats, coyotes and snakes.

Although divers and cadaver dogs were brought in, it wasn't until the heavy late-summer rains stopped and the water receded that Laundrie's remains and a backpack and notebook belonging to him were found with his father's help.

Officials have not released the cause of death for Laundrie or said whether a note or other evidence about Petito was found.

Are Laundrie's parents in legal trouble?

Prosecutors could look into obstruction of justice charges against the parents if they hid their son, but it would not be an easy case to prove, legal experts said. Petito's body hadn't yet been found during the time he was home.

"That's a steep hill to climb," Garcia said. "How can you establish they knew he committed the crime? Did they intentionally help him avoid detection and arrest? You have to establish knowledge and intent."

Laundrie's parents have not given any media interviews and initially referred law enforcement officials to their attorney, Steven Bertolino. He said the parents cooperated with investigators and are "heartbroken" over the entire situation.

Before he disappeared, Laundrie would not talk to the police, on the advice of his lawyer.

Will there be repercussions for Utah police?

The police department in Moab, Utah is conducting an internal review of officers' actions when Petito and Laundrie were stopped on August 12 after the two got into a scuffle.

Police body-camera video showed a distraught Petito describing a fight that escalated. A police report concluded she was the aggressor, but the only injuries consisted of a few scratches. Officers decided to separate them for the night rather than file any charges.

The question is whether the Moab officers followed policy and, if not, whether that led to further violence and possibly Petito's slaying.

What about 'missing white women syndrome'?

Much was made in the media about the intense interest in Petito's case compared with the scant attention paid to numerous missing-persons cases involving women of colour.

Native American women, in particular, generate little media coverage when they disappear.

In Wyoming, where Petito was found, just 18 per cent of cases of missing indigenous women over the past decade had any media mentions, according to a state report released in January.

Brian Laundrie was wanted over the disappearance of his girlfriend, Gabby Petito. Photo / Instagram

One sample of 247 missing teens in New York and California found 34 per cent of white teens' cases were covered by the media, compared with only 7 per cent of Black teens and 14 per cent of young Latinos, according to Carol Liebler, a communications professor at Syracuse University.

"What's communicated is that white lives matter more than people of colour," she said.

Petito's father, Joseph Petito, said the Gabby Petito Foundation is in the formative stages and will seek to fill in any gaps that exist in the work of finding missing people.

"We need positive stuff to come from the tragedy that happened," he said. "We can't let her name be taken in vain."