(1) Where a person, having a previous conviction for a crime, is again convicted of a crime, he or she shall be liable to increased punishment in the manner provided in Part 1 of the Table in Schedule 6 to this Code.
(2) Unless otherwise provided in this Code or any other enactment—
(a) a previous conviction shall not be admitted in evidence against a person except within the period specified in Part 2 of the Table after the expiration or execution of the sentence passed on that person upon the previous conviction, or of any sentence to which that sentence has been commuted;
(b) nothing in this section, or in the Table, shall exempt a person from any liability to which he or she may be subject under this Code to death or to any greater or other punishment than the punishment prescribed in the Table, and any other different punishment to which he or she is liable under this Code may be inflicted in addition to the punishments prescribed in the Table;
(c) nothing in this section, or in the Table, shall apply to libel, or to any act which is a crime on the ground of negligence, or to any offence punishable on first conviction by fine only.
(2) A conviction of a person for a crime committed by him or her before attaining the age of 18 years shall not be admitted in evidence against him or her after he or she has attained the age of 21 years.