His sister, Monique is also accused of participating in the attack and will stand trial seperately.
Coates said Brittney's stomach and liver had been punctured and stab wounds that severed her spinal cord have left Brittney a paraplegic for the rest of her life.
Wiederrick, of Hailey, left a party at the Sigma Alpha Epsilon fraternity house about 2am Sunday and called his roommate to say he was walking home.
however, police say he never made it back to his Theophelius Tower residence hall on the university campus.
" She said she took the question as meaning Monique Maestas wanted to hurt her because she had been an eyewitness.
Bantam said although Beau didn't answer Monique, he made "efforts to protect me." She said the biggest effort was made when Beau decided to pull over instead of trying to escape from police cars pursuing them in Utah.
Last Friday Maestas pleaded guilty to one count each of murder, attempted murder and burglary, all with use of a deadly weapon, in the killing of 3-year-old Kristyanna Cowan and the stabbing of her half-sister, Brittney Bergeron, in a trailer in the Casa Blanca hotel RV park.