That trip from 6 to 8 September 2021, after Laundrie had already killed Ms Petito, and the lack of cooperation with her missing persons enquiry, are at the centre of a lawsuit Ms Petito’s parents filed in the Sarasota County Circuit Court in Venice, Florida.
The Petitos allege that Chris and Roberta Laundrie not only knew that their 23-year-old son had murdered his girlfriend but that they knew the location of her remains.
Instead of coming forward with the information, the family went on a last trip together to the campsite roughly 75 miles from their home in North Port, the suit alleges.
Joe Petito and Nichole Schmidt also accuse the Laundries of planning to help Brian leave the country, and are seeking damages for the “intentional infliction of emotional distress”.
The lawsuit alleges Brian Laundrie informed his parents of Ms Petito’s murder “on or about” 28 August.
“While Joseph Petito and Nichole Schmidt were desperately searching for information concerning their daughter, Christopher Laundrie and Roberta Laundrie were keeping the whereabouts of Brian Laundrie secret, and it is believed were making arrangements for him to leave the country,” the lawsuit says.
On Wednesday, Judge Hunter W Carroll will hear arguments from both sides to determine whether the case can proceed to a jury trial, which is scheduled for August next year.
Florida attorney Pat Reilly will represent the Petito family, who are seeking $100,000 in damages.
Matthew Luka will appear as a defence attorney for the Laundries, who are seeking to have the suit dismissed.
Their family attorney Steve Bertolino is also expected to appear via video link.
Ms Schmidt has also filed a separate wrongful death claim seeking $30,000 in damages from Laundrie’s estate.
She states in the suit that Laundrie intentionally killed her 22-year-old daughter, causing her and her ex-husband Joseph Petito to incur funeral and burial expenses, and suffer “a loss of probable future companionship, society and comfort”.
Ms Petito and Laundrie set off from Long Island on a trip across the United States in July last year.
They were pulled over by police officers in Moab, Utah, on 12 August after an eyewitness saw Laundrie strike Ms Petito.
Despite evidence of a domestic assault, police separated the pair for one night before allowing them to continue on their journey.
Laundrie returned home from his trip without Ms Petito on 1 September and later disappeared, kicking off a nationwide search for the vlogger and – after her remains were discovered in the forest – a nationwide manhunt for him.
Laundrie is believed to have strangled Ms Petito in the Bridger-Teton National Forest between Yellowstone National Park and Grand Teton National Park in Wyoming, according to the FBI.
Laundrie then went missing. His skeletal remains were discovered at the Carlton Reserve on 20 October near his backpack, notebook and items of clothing.
He appears to have died by suicide from a self-inflicted gunshot wound to the head.
Laundrie confessed to murdering his girlfriend in the notebook found next to his remains, the FBI said.