Pleas to an indictment or information are:
A defendant who does not plead guilty may enter one or more of the other pleas. A defendant who does not plead not guilty by reason of insanity is conclusively presumed to have been sane at the time of the commission of the offense charged. The court may, for good cause shown, allow a change of plea at any time before the commencement of the trial.
R.C. §2943.03