By Laura Zuckerman
April 4 (Reuters) - A snowboarder who inadvertently triggered a deadly avalanche that engulfed a Montana home in February will not face charges for riding a mountain slope that was closed to the public at the time, prosecutors said on Friday.
The avalanche that tore down a mountainside and into a Missoula neighborhood leveled the two-story house of an elderly couple several blocks from the University of Montana campus, burying them and two neighbor children in snow.
All four were found alive in the massive debris field, but 68-year-old textile artist Michel Colville later died of her injuries. An investigation by the West Central Montana Avalanche Center found the avalanche was triggered by a snowboarder who was able to ride the slide to safety.
The snowboarder had been part of a sledding party of four drawn to the mountain by fresh snow brought by a blizzard that had closed the campus earlier that day, said Missoula City Attorney Jim Nugent.
The snowboarder ventured onto a slope that was off-limits for recreational use to protect a wintering elk herd but did not see the city's small sign warning of the closure, likely because of blowing snow, Nugent said.
A probe by Missoula police recommended against filing trespass charges against the snowboarder because it would require proof that he knowingly violated the law, said Nugent.
"The police felt there was not sufficient evidence to prove the snowboarder committed the violation beyond a reasonable doubt and we don't have any evidence to counter what the police recommendations are," Nugent said.
Almost all U.S. avalanches that affect people strike in the backcountry of the mountainous West and are caused by snowmobilers, skiers and snowboarders who inadvertently trigger them. Avalanches have killed 26 people so far this season, records show. (Editing by Cynthia Johnston and Andrew Hay)