This chapter examines how scientific evidence is translated into legitimate, actionable policy during emergencies. It maps the science–policy interface (advisory panels, incident science groups, hybrid models) and the roles scientists play—from issue advocate to honest broker—under conditions of time pressure and uncertainty. We outline practical translation steps (risk framing, numeracy aids, metaphors, and uncertainty visualization), then show how decision tools (trigger points, scenario planning, Bayesian updating) support precaution without sacrificing credibility. Public skepticism is treated as a predictable response shaped by experience, culture, and media, addressed through co-production, citizen science, and participatory briefings. Ethical tensions (duty to warn vs. privacy, information equity, protection from politicization, provenance) are operationalized into procedures that make advice auditable. Finally, we link science to policy instruments—advisories, thresholds, zoning, compensation—paired with evaluation metrics for adaptive management. Nuclear mini-cases illustrate why technical choices and communication cadence must move in lockstep to sustain trust and compliance.