A U.S. tank company commander pleaded not guilty Monday as he went on trial on charges related to the killing last year of a critically wounded Iraqi. Capt. Rogelio Maynulet, 30, from Chicago, could face a maximum sentence of 20 years and three months if convicted of assault with intent to commit murder. Maynulet, wearing full dress uniform, stood as his lawyer, Capt. Will Helixon, entered his plea. The judge in the case, Col. James Pohl, threw out a second charge of dereliction of duty after the defense argued that prosecutors had not specified which duty he neglected.