unjust enrichment doctrine

General principle that one person should not be permitted unjustly to enrich himself at expense of another, but should be required to make restitution of or for property or benefits received, retained or appropriated, where it is just and equitable that such restitution be made, and where such action involves no violation or frustration of law or opposition to public policy, either directly or indirectly. Tulalip Shores, Inc. v. Mortland, 9 Wash.App. 271, 511 P.2d 1402, 1404.

Unjust enrichment of a person occurs when he has and retains money or benefits which in justice and equity belong to another. L & A Drywall, Inc. v. Whitmore Const. Co., Inc., Utah, 608 P.2d 626, 630.

Three elements must be established in order to sustain a claim based on unjust enrichment: A benefit conferred upon the defendant by the plaintiff; an appreciation or knowledge by the defendant of the benefit; and the acceptance or retention by the defendant of the benefit under such circumstances as to make it inequitable for the defendant to retain the benefit without the payment of its value. Everhart v. Miles, 47 Md.App. 131, 136, 422 A.2d 28.

See also quantum meruit