The Supreme Court has explained following four conditions are required for the applicability of the doctrine of res judicata between co-defendants.
“(1) there must be a conflict of interest between the defendants concerned;
(2) it must be necessary to decide the conflict in order to give the reliefs which the plaintiff claims;
(3) the question between the defendants must have been finally decided; and
(4) the codefendants were necessary or proper parties in the former suit.”