The family of Gabby Petito said they would file a $50m (£41.4m) wrongful death lawsuit against Utah police on Monday, claiming officers failed to recognise their daughter was in danger.
Ms Petito’s strangled body was discovered in September on the edge of Grand Teton National Park in Wyoming.
Her boyfriend, Brian Laundrie, admitted killing her in a notebook discovered near his body in a Florida swamp, where he took his own life.
A month before, police in the small town of Moab, Utah, had stopped the couple, with body cam footage showing a visibly upset Ms Petito.
Officers allowed the couple to continue on a cross-country van journey despite her distress with Laundrie, after requiring them to spend a night apart.
The pending lawsuit will allege officers failed to recognise that the 22-year-old was in danger and in need of help.
Speaking at a press conference on Monday, her mother Nichole Schmidt said tearfully of the video: “I wanted to jump through the screen and rescue her”.
After the notice of claim was filed, Moab city government spokesperson Lisa Church declined to comment, saying officials do not comment on pending litigation.
Moab officials have 60 days to respond before the family can file a lawsuit based on the claim.
The family’s lawyer, James McConkie, told reporters in Salt Lake City that “the officers failed to recognise the serious danger that she was in, and failed to investigate fully and properly.”
He added: “They did not have the training that they needed to recognise the clear signs that were evident that morning, that Gabby was a victim and that she was in serious need of immediate help."
Public workers such as police officers typically have some protection from lawsuits in many US states, including Utah.
However, the family’s lawyers said they planned to argue that applying Utah’s governmental immunity law to wrongful death claims is unconstitutional.
Earlier this year, an independent investigation found that police in Moab made “several unintentional mistakes" when they came across Petito and Laundrie.
The report found it was very likely that Petito “was a long-term victim of domestic violence, whether that be physically, mentally, and/or emotionally".