This paper draws on several recent cases to analyse the particular challenges for experts who are called to provide scientific advice under time-critical circumstances. It uses the notion of civic epistemologies (Jasanoff, 2005) to consider the testing of knowledge claims in time-pressured situations. It argues that an interdisciplinary approach that incorporates diverse perspectives is needed to manage these high-stakes crises. This poses a major challenge: time-critical crises do not allow for the identification of key experts and of stakeholders – as is typically the case for the assembling of expert advisory groups for non-time-critical issues. These issues have again arisen in the COVID-19 pandemic in 2020, but not for the first time, and flexible cross-case, cross-discipline learning provides a means of enhancing resilience for future emergencies. There are some critical lessons to be learned in this crisis from other situations involving high stakes and rapid response. This paper uses its case studies to build a framework for analysing the roles of experts in emergencies, and suggests that understanding the power dynamics inherent in these situations is critically important in the context of the Sendai Framework.