Manuel Diaz was found guilty by the judge in the case Friday after entering the plea. The 26-year-old Diaz will be sentenced May 22.
Diaz, a detention deputy at the time, punched county jail inmate Edgar Richard multiple times in a cell. Richard suffered serious head and jaw injuries in the incident, which happened after the inmate cursed an aide and threw medication on the floor.
Diaz was fired after the incident. He had been a detention deputy about four years.
An attorney for Richard said the injured man _ now in his early 60s and in a nursing home _ still can't shallow and chew and is being fed by a tube.
(Copyright 2009 by The Associated Press. All Rights Reserved.)