By linking the realms of public policy-making, science and the public, advisory committees that include academics, state representatives and societal stakeholders answer to a double challenge that governments face today: a need for technical knowledge and an increasing demand for public acceptance and accountability. In contrast to purely scientific policy advice, little theoretical attention has so far been paid to these hybrid advisory committees. Drawing on and adapting research on knowledge utilisation, theories of delegation, decision-making and governance, an analytical framework of the use of multi-source, negotiated expertise will be developed and applied to four cases set up by the German Federal Government with mandates in social policy and in science and technology policy. The study shows the committees’ pronounced governance potential, which builds on their political and epistemic authority. It describes two distinct dynamics that lend the committees to instrumental, problem solving, and symbolic, substantiating purposes.