Section 8. If a person whose name has been so placed in the jury box has been convicted of any felony, or of any other offence punishable by imprisonment in a jail or house of correction for more than one year, or is guilty of gross immorality, or is found by the justice holding court to be unqualified or unfit to serve as a juror, he may be relieved by said justice from sitting in any case, or his name ordered by the justice to be stricken from the jury list.