(Portland, OR)  --  A man accused of opening fire inside the Foster Farms food plant in Corvallis might plead not guilty by reason of insanity.  Court documents show that lawyers for 22-year-old Adrian Nickerson of Albany are working on a possible insanity defense.  Nickerson is accused of threatening to blow up the building and then opening fire inside a women's restroom at the plant on July 18th.  No one was injured.  Police say Nickerson was a temporary employee at the plant.