A Butte County man who killed a pedestrian last year has entered a guilty plea. In October, 65-year-old William Mandril was impaired by drugs while driving when he hit three people who had stopped to help a driver with a disabled vehicle. The collision killed 20-year-old Hillary Wilhite of Oroville and seriously injured the other two. Mandril failed a series of field sobriety tests, had difficulty staying awake, refused alcohol screening at the scene and claimed to have no memory of the accident. After the collision Mandril tried to discard a large bag of marijuana and other drug paraphernalia. Further investigation revealed the presence of methamphetamine, oxycodone, carisoprodol and meprobamate in Mandril’s blood, but no alcohol. On Tuesday, he pled guilty to felony vehicular manslaughter with special allegations. Mandril faces six years in state prison. he’s currently out on bail awaiting sentencing.