The principle that a party who has obtained a judgment by FRAUD on the court cannot rely on res judicata - established in S.P. Chengalvaraya Naidu
v. Jagannath - stands for the proposition that:

Explanation: In S.P. Chengalvaraya Naidu v. Jagannath the Supreme Court held that a party who has obtained a decree by suppres.sion of the very document on which his title depended has perpetrated fraud on the court, and that 'fraud unravels all' - such a decree is a nullity and no res judicata protects it. The case is the leading authority that res judicata cannot shield a judgment procured by fraud or collusion. It shows that conclusiveness has boundaries and judicial integrity trumps procedural finality. This makes it a pivotal CPC/civil-procedure precedent