“This interpretation leads to a reading of πάντες ἥμαρτον (“all sinned”) that is itself improbable. In the Augustinian interpretation, this refers to the whole human race sinning in Adam in a collective and participatory way. As Augustine himself puts it, “all have broken God’s covenant in that one man in whom all sinned.” The idea is that Paul speaks of an involuntary participation in Adam’s sin by an actual participation in Adam’s nature. Adam is not simply an individual, but the primal instantiation of human nature, and so the consequences of his fall not only affect him personally but also affect all his descendants subsequently and distributively.47 In our estimation, the theological underpinnings of this view are not in themselves objectionable; indeed, one can find precedent in Scripture for such a manner of thinking (see Heb 7:6–10). Nevertheless, the fact remains that, in his letters, Paul consistently uses the verb ἁμαρτάνω (“to sin”) for actual sins committed by morally responsible persons in the course of their individual lives. That he has this default meaning in mind in Romans 5:12d is nearly certain: earlier in the letter he uses the identical Greek expression to insist that “all have sinned [πάντες ἥμαρτον] and fall short of the glory of God” (Rom 3:23)—an unmistakable reference to the universal occurrence of actual sins—and two verses later, in a passage intended to preempt objections to 5:12, Paul speaks of multiple generations of “those whose sins [τοὺς … ἁμαρτήσαντας] were not like the transgression of Adam” (5:14). For these reasons, the translation “in whom” falters on linguistic grounds.”
Hahn, S. W., & Mitch, C. J. (2017). The Diffusion of Death: Romans 5:12 and Original Sin. Letter & Spirit, 12, 28.