Appearing in an Alameda County courthouse under high security, Mesherle entered the plea through his attorney.
His trail date was set for Oct. 13, but Mesherle's lawyer, Michael Rains, told Judge Morris Jacobsen that he will seek a change of venue in the high-profile case.
Mesherle shot and killed 22-year-old Oscar Grant on the Fruitvale Bart station platform shortly after 2 am on Jan. 1. He quit the Bart police force following the shooting without speaking to investigators. His lawyer has argued that the shooting was a mistake and that Mesherle intended to use his Taser.
Rains was admonished today for appearing to violate a gag order that bars lawyers in the case from speaking to the media.
Jacobsen held up a recent newspaper article which quoted Rains and said "I want to caution both sides: Mind yourselves when you talk to the press."