DEER LODGE, Mont. -

A jury has convicted a Montana State Prison inmate of killing another prisoner with a weapon made out of two razor blades and a pen.
    
The guilty verdict means 30-year-old Shaun Duncan Morrison faces life in prison for the attack against Julio Santiago Jr. over a pair of stolen earphones.
    
Butte District Judge Brad Newman ordered a pre-sentence investigation before setting a sentencing date.
    
The 53-year-old Santiago died after the September 2011 attack that involved punching, choking and cutting his face and neck.
    
The Montana Standard reports (http://bit.ly/T6mltp0 ) Morrison pleaded not guilty and did not testify. His attorney says Morrison's troubled past and prison culture led to extreme emotional and mental stress.
    
The jury rejected that defense with its verdict.
    
Santiago's death was the prison's first murder in 16 years