Is it ensure, insure, or assure?
"pertaining to or suitable for courts of law," 1650s, from Latin forensis "of a forum, place of assembly," from forum "public place" (see forum). Used in sense of "pertaining to legal trials," as in forensic medicine (1845). Related: Forensical (1580s).
forensic fo·ren·sic (fə-rěn'sĭk, -zĭk)
Relating to, used in, or appropriate for courts of law or for public discussion or argumentation.