In recent years, scholars in science and technology studies have examined the advice that experts make for the governance of biomedicine. This STS scholarship, however, has not yet explained how the credibility of ethics expertise in public bioethics is produced from particular conditions and extended to different settings. This article describes how a bioethics commission created the ethical principle of justice and examines how the ethics expertise established public credibility on the justice principle. The findings suggest that the principle of (...) justice was first explored as the diverse concepts of “equality” with reference to the review of fetal research, redefined as “fairness” or “desert” from theoretical viewpoints, and then circulated as a standard framework in local settings. The credibility of ethics expertise, based on the coproduction of material and moral orders, was made possible by reaching common ground among different data, principles, and background theories. (shrink)