Whenever any person shall plead guilty to an information filed against him in any court, it shall be the duty of the judge of such court, before pronouncing judgment or sentence upon such plea, to become satisfied after such investigation as he may deem necessary for that purpose respecting the nature of the case, and the circumstances of such plea, that said plea was made freely, with full knowledge of the nature of the accusation, and without undue influence. And whenever said judge shall have reason to doubt the truth of such plea of guilty, it shall be his duty to vacate the same, direct a plea of not guilty to be entered and order a trial of the issue thus formed.
MCL 768.35