“1. Declarative (judicial) meaning
Among biblical scholars it is generally recognized, even by Roman Catholics and Protestants unsympathetic to the Reformation doctrine, that the verb to justify means “to declare righteous.” It is a forensic (legal) term taken from the courtroom. This is the case in the Old Testament (tsadaq). And it is just as true in the New Testament: dikaioō, “to declare just,” is unmistakably judicial in character. This verb was erroneously rendered iustificare (to make righteous) in the Latin Vulgate, and this mistake contributed significantly to the idea of justification as a process, synonymous with sanctification.
Though hardly motivated by doctrinal concerns, Erasmus had pointed out these translation errors even before Luther. A number of Roman Catholic New Testament scholars have pointed out in recent years that dikaioō has to do with legal vindication. The lexical definition of to justify is “to be cleared in court,” which, as Sanders has said above, is found even in the Old Testament (tsadaq and cognates) and can be amply attested. That significant consensus can be reached on this point even among those who stand in some critical relation to the Reformation interpretation demonstrates that we are quite far from witnessing the destruction of a forensic definition of justification on exegetical grounds.
While the verb is judicial or forensic (that is, referring to a declaration rather than a process), this fact by itself does not indicate the basis on which or the means by which one is justified before God. It simply stipulates that the demands of the law have been fully met (Ac 13:39; Ro 5:1, 9; 8:30-33; 1Co 6:11; Gal 2:16; 3:11). In Scripture, the opposite of justification is not corruption but condemnation, which is quite evidently a judicial concept as well (Jn 3:17-18; Ro 4:6-7; 8:1,33-34; 2Co 5:19). (291 Ch:Justified and Adopted)
Taken from Michael Horton’s Pilgrim Theology: Core Doctrines for Christian Disciples
Section 2 covers “The righteousness of God” and section 3 covers “Imputed righteousness.”