Can we assume that the Noun in the nominative case is always the subject of the phrase or sentence?
It should be a predicate nominative: ἡ ἁμαρτία ἐστὶν ἡ ἀνομία. (1 John 3:4b)
In Chapman & Shogren's Greek New Testament Insert there are 6 uses listed for the nominative case with some brief examples. The subject would be the most recognized along with its use as a predicate nominative.
