No person shall be qualified to sit as a juror in any justice or police court of Wayne county, or on an inquest before any coroner, who has already sat as a juror in said justice or police court, or on an inquest before said coroner, more than 3 times during the calendar year next preceding the time when he is summoned or offered as a juror on said court, or on said inquest. And it shall be the duty of justices of the peace, and police justices and coroners, to enforce and carry out the provisions of this law, and to discharge any such juror. It shall be a good cause of challenge, over and above all challenges otherwise allowed by law, that any person summoned or offered as a juror, shall have acted as juror in the same tribunal or court, more than 3 times during the prior calendar year.