This article argues for a dependency between structural Case and phasal domains and against Case values as intrinsic properties of (C)-T and (v*)-V. Rather, Nominative or Accusative values are derived compositionally from properties of the entire Probing domain: (i) NOM occurs whenever the Probing domain is specified as [uD, u], while (ii) ACC is assigned if the Probing domain is specified as [uD]. The presence of a [uCase] feature is assumed on all DP arguments, whether null or overt. However, after Case valuation, DPs with inherent intensions and extensions will be lexicalized but variables, such as PRO, will not. The analysis focuses on DP subjects (both lexical and PRO) in non-finite CPs, and relies on availability of null expletive pro as a UG primitive. It assumes Chomsky's Feature Inheritance Model (Chomsky