On July 7, investigators suspect Carter was under the influence of alcohol when the truck he was driving veered off Pondtown Road, near Scofield in Carbon County, about 1:45 a.m.
Carter and his passenger, 22-year-old Brooke Tomadakis, were ejected as the truck rolled down a 150-foot embankment.
Tomadakis died at the scene. Carter also had another passenger, Chad Wink, who survived, said Carbon County Attorney Gene Strate.
No one was wearing seat belts, Strate said.
A driver who had been behind the truck saw the accident and tried to call for help. When his phone did not work in the remote area, he drove to a gas station and called from there, Strate said.
Carter's blood-alcohol level tested at slightly above the legal limit of 0.08 percent, Strate said. Prosecutors were waiting on the results before filing charges.
Carter's first court appearance is scheduled for Oct. 21 before Judge George Harmond.
Besides several traffic citations, Carter's criminal record is a short one. He was convicted of attempted aggravated assault, a misdemeanor, in 2005.
Tomadakis' funeral was held July 11 at Notre Dame de Lourdes Catholic Church. She loved the outdoors and to dance, according to an obituary.
"We will always remember her laughter, bright smile, and her crazy, goofy [and] bubbly personality," the obituary reads. "Nobody else could change a mood faster than Brooke."