(1) In any proceedings involving an apportionable claim (a) the liability of a defendant who is a concurrent wrongdoer in relation to that claim is limited to an amount reflecting that proportion of the damage or loss claimed that the court considers just, having regard to the extent of the defendant's responsibility for the damage or loss; and(b) the court is not to give judgment against the defendant for more than that amount.(2) If the proceedings involve both an apportionable claim and a claim that is not an apportionable claim (a) liability for the apportionable claim is to be determined in accordance with the provisions of this Part; and(b) liability for the other claim is to be determined in accordance with the legal rules, if any, that (apart from this Part) are relevant.(3) In apportioning responsibility between defendants in the proceedings (a) the court is to exclude that proportion of the damage or loss in relation to which the plaintiff is contributorily negligent under any relevant law; and(b) the court is to have regard to the comparative responsibility of any concurrent wrongdoer who is not a party to the proceedings.(4) This section applies in proceedings involving an apportionable claim whether or not all concurrent wrongdoers are parties to the proceedings.(5) A reference in this Part to a defendant in proceedings includes any person joined as a defendant or other party in the proceedings (except as a plaintiff) whether joined under this Part, under rules of court or otherwise.