determinative

1. (law) Sufficient to decide something (such as a question of fact or of law).Examples: "When assigning custody, the preference of the child will be considered, but it is not determinative."; "This proceeding, though not presenting questions difficult of determination, or points of law that are novel, is unusual in many of its features, and is important as determinative of the disposition and welfare of a number of little children, ignorant of the contest that is being carried on in regard to them."; "It is therefore clear that, even in adoption cases where it might play a more important role, race is not a determinative factor and its importance will depend greatly on the facts."