A teenage boy has been sentenced to life in prison after being convicted of raping and killing a 5-year-old girl in Southern Oregon. Judge Randy Garrison said yesterday in Roseburg that 18-year-old Dustin Wallace poses too great a risk to the public to ever be allowed free. Wallace was 16-years-old in 2010 when he killed 5-year-old Sahara Dwight. He was visiting his father, who was living with the girl's mother. His attorneys said Wallace has suffered from mental health problems since he was five.