The Ohio prison inmate accused of sending a Franklin County judge a suspicious letter and powder in an anthrax hoax and instructing a second inmate to do the same has pleaded guilty. 33-year-old Sean Heisa will serve three additional years on top of his 30-year term for a series of armed robberies. The letters were sent last year. Heisa is an inmate at the Southern Ohio Correctional Facility in Lucasville