Constructive res judicata cannot be invoked to bar ownership claims over land parcels distinct from those previously litigated.

In 1960, Mahabir Rai transferred 95.80 acres of land to his mother and his son, the appellant.

In 1962, a General Power of Attorney (GPA) was executed in favor of Rambhajan (respondent's predecessor), who used it in 1969 to sell two portions of the land (21.43 acres and 33.76 acres) to third parties.

The appellant (as a minor through guardians) unsuccessfully filed two prior suits seeking the cancellation of these specific sale deeds.

In 1985, Rambhajan sought to mutate his name in revenue records for the remaining land, prompting the appellant to file the present suit for declaration of title and possession of the 43.69 acres remaining after the 1969 alienations.

The High Court set aside the lower courts' decrees, dismissing the suit on the ground that it was barred by the doctrine of constructive res judicata.

1. Whether the present suit for declaration of title and possession was barred by the principle of constructive res judicata under Section 11, Explanation IV of the CPC.

2. Whether the appellant "might and ought" to have raised his claim of ownership over the entire property based on the 1960 sale deed in the earlier litigations which were limited to challenging specific sale deeds.

Section 11 of the Code of Civil Procedure, 1908, specifically Explanation IV, which defines "constructive res judicata" as any matter which might and ought to have been a ground of attack or defense in a former suit.

The rule is based on public policy to prevent individuals from being "vexed twice" for the same litigation, as established in Henderson v. Henderson and Daryao v. State of U.P.

The principle that "ought" implies a threshold above mere possibility and requires "reasonable diligence".

The Court reasoned that the High Court erred in its premise that the appellant was required to assert his ownership over the entire 95.80-acre parcel in previous suits that were limited to challenging specific unauthorized sale deeds.

The Court noted that since the appellant’s title over the larger parcel was undisputed by the 1960 deed, there was no occasion or "legitimate purview" to litigate his entire title until the respondent attempted to mutate the remaining land in 1985.

The Court observed that the "might and ought" rule must be applied with regard to the "ambit of the earlier proceedings" and the "nexus" of the controversy; here, the earlier suits were defensive actions against specific threats to the property, whereas the current suit was a response to a new threat to the remaining land.

The Court further emphasized that applying constructive res judicata in a way that leads to "unduly harsh and unjust" consequences in family disputes is offensive to law and equity.

The Court restored the appellant's right to pursue his claim for declaration of title and possession of the remaining 43.69 acres.