Law reform bodies frequently express a commitment to making their law and policy recommendations evidence-based. They also readily endorse the importance of the transparency and democratization of their processes. They do not seem, however, to connect these two goals of evidence-based policy and transparency. This stands in contrast to the ongoing revolution in several fields of research towards open synthesis and science, which envisions transparency and open access as a means to improve the reliability of science. In this article, we suggest that several recent concerns and controversies surrounding evidence-based law reform, such as allegations of bias among officials, can be addressed through open synthesis and science. We include a novel study of 22 research syntheses commissioned by the Royal Commission into Institutional Responses to Child Sexual Abuse, finding uneven adoption of even the most basic transparency measures. We end with five proposals that advance open evidence-based law reform, including law reform bodies requiring that commission reports follow basic reporting guidelines and greater disciplinary diversity among law reform staff.