The health crisis caused by the SARS-CoV-2 pandemic has put the system of expert opinion to the test both in France and abroad. As a result, certain analyses or recommendations have been criticized or challenged by citizens or politicians, with the rise of news channels and social media fostering confrontation rather than consensus-building. It is therefore important to return to the fundamentals of expert opinion. While the analysis of scientific data forms the basis for building expert opinion, evidence alone cannot be the sole element of this process. Other steps play a fundamental role: the regulatory framework, the recruitment of experts, quality control, validation, and the public dissemination of opinions are all factors that contribute to the quality of the opinions and recommendations produced. It is only when these various conditions are met—including in times of crisis—that the results of expert assessments can be considered as expert opinions rather than merely the expression of individual or collective views.