Analyses the operation of the mutual wills doctrine, whereby a constructive trust binds the survivor to the terms of the testators' agreement, including: (1) the minimum requirements of this agreement; (2) the parties' latitude to define its terms; (3) the challenges of establishing the agreement; (4) whether the doctrine requires a "contract at law"; (5) the need to show that either party relied on the agreement; and (6) the causative events
