Johannes Mehserle, the ex-BART officer who shot and killed Oscar Grant on New Year's Day, pleaded not guilty yesterday to murder. During a "tense" hearing, Mehserle "entered court for about three minutes ... spoke only to say 'yes' three times, in response to questions from Judge Robert McGuiness about whether he waived his rights to a speedy trial," according to the Chronicle. He is currently being held without bail at Santa Rita Jail over in Dublin.