A constructive trust arises by operation of law, without regard to the intention of the parties to create a trust. It does not require a deed signifying the institution of trust. Under a constructive trust, the trust arises by operation of law as from the date of the circumstances which give rise to it. The function of the court is only to declare that such a trust has arisen in the past.
Constructive trust can arise over a wide range of situations. To quote Cardozo, J., “a constructive trust is a formula through which the conscience of equity finds expression”.
Story on Equity Jurisprudence has explained “Constructive Trust” as: “One of the most common cases in which a Court of equity acts upon the ground of implied trusts in invitum, is where a party has received money which he cannot conscientiously withhold from another party. It has been well remarked, that the receiving of money which consistently with conscience cannot be retained is, in equity, sufficient to raise a trust in favour of the party for whom or on whose account it was received. This is the governing principle in all such cases. And therefore, whenever any controversy arises, the true question is, not whether money has been received by a party of which he could not have compelled the payment, but whether he can now, with a safe conscience, ex aequo et bono, retain it. Illustrations of this doctrine are familiar in cases of money paid by accident, or mistake, or fraud. And the difference between the payment of money under a mistake of fact, and a payment under a mistake of law, in its operation upon the conscience of the party, presents the equitable qualifications of the doctrine in a striking manner. It is true that Courts of Law now entertain jurisdiction in many cases of this sort where formerly the remedy was solely in Equity; as for example, in an action of assumption for money had and received, where the money cannot conscientiously be withheld by the party; following out the rule of the Civil Law; Quod condition in debiti non datur uitra, quam locupletior factus est, qui accepit. But this does not oust the general jurisdiction of Courts of Equity over the subject-matter, which had for many ages before been in full exercise, although it renders a resort to them for relief less common, as well as less necessary, than it formerly was. Still, however, there are many cases of this sort where it is indispensable to resort to Courts of Equity for adequate relief and especially where the transactions are complicated, and a discovery from the defendant is requisite.” Janardan Dagdu Khomane v. Eknath Bhiku Yadav, (2019) 10 SCC 395.