Alyssa Byrne, the 19-year-old from Petaluma found dead last week in South Lake Tahoe, apparently took a wrong turn New Year's Eve and wandered a short distance through snow before shedding her ski jacket and dying in the bitter cold on a snowbank, authorities said Monday.
Byrne was found dead three days later. Her boot prints -- the only ones in the vicinity -- suggested disorientation that may have been caused by alcohol consumption, hypothermia or both, El Dorado County Sheriff's Lt. Pete Van Arnum said.
"I don't want to speculate," he said, although he confirmed investigators had reports Byrne had been drinking while in town with friends for a music festival.
He noted advanced hypothermia causes confusion and deteriorating cognition. Victims can become disoriented and lose judgment.
"It was subzero that night and, depending on how long she was out in the cold, that could have affected her," Van Arnum said.
Experts say it's common for those with fatal hypothermia to remove clothing shortly before death because of physiological changes that cause a spreading sense of warmth.
The National Weather Service said it was minus 8 degrees overnight New Year's Eve in the area.
It's unclear when Byrne died. The Sacramento County Coroner's Office, which is handling the death investigation, has put the official date at Jan. 4, the day she was found. Authorities have said there were no signs of traumatic injury or foul play.
Douglas County, Nev., investigators, who led the initial search for Byrne, said she last used her cellphone at 11:53 p.m. New Year's Eve and was believed to have collapsed after leaving the final concert of a three-day music festival at Lake Tahoe Community College, a half-mile from where her body was found.
The 2011 Casa Grande High School graduate had driven Dec. 29 to Lake Tahoe with three friends with whom she attended the festival and shared a room at the Horizon Casino Resort in nearby Stateline, Nev.
But on New Year's Eve, she got ahead of her companions in a concert crowd and disappeared around 11 p.m., friend and former classmate Jay Donnellan said.
Byrne told Donnellan by phone at 11:23 p.m. that she was taking a shuttle bus back to the Horizon. He never saw her again.
For the next three days, family and friends conducted a frantic search for her.
Her body was spotted Friday morning by a public utility worker who was perched on a bucket truck and able to peer over a 4-foot-high snow bank that had hidden her from motorists and others.
Byrne was about 10 feet off Pioneer Trail, near Al Tahoe Boulevard, which leads to the junior college and runs between Pioneer Trail and Highway 50.
Authorities said long shuttle bus lines may have caused her to join others who decided to walk back to Stateline along an about four-mile route that would have followed Al Tahoe Boulevard and then turned to the northeast along Pioneer Trail. It also is possible she walked through the campus instead of taking a bike path used by others, Van Arnum said.
But her final location indicated she turned right on Pioneer Trail, rather than left as would be expected, and walked along the road before climbing the berm of frozen snow, Van Arnum said.