Article 31(1)(d)1 of the Rome Statute of the International Criminal Court (ICC Statute) presents an important opportunity to reconsider the defence of duress in cases of unlawful killing. While the case of Erdemović has done much to substantiate the existence of the defence of duress at international law it appears to have curtailed the doctrine by interpreting it with reference to a strict form of proportionality characteristic of duress as justification. On the other hand, duress as excuse requires some measure of proportionality. This article will contend that the hybrid approach of Nuremberg Military Tribunals (NMTs), defined duress and the moral choice test primarily by reference to culpa in causa, not resorting to duress, and a ‘softer’ proportionality and in doing so, provided a more flexible and workable model for duress. Article 31(1)(d) of the ICC Statute, although an interesting attempt to find the balance between duress as excuse and justification, is a missed opportunity to redefine the defence in international criminal law. An alternative test for duress, with reference to the principles that emerged from the jurisprudence of the NMTs, is required in order to find the correct balance between duress as excuse and justification.