Questions regarding the construction of mathematical authority have implications for learning, specifically for students' views of themselves as mathematics learners and doers with valuable contributions. We consider the ideas proposed by eight first-grade students who had the most airtime during 12 lessons of a classroom teaching experiment. We noted when ideas were proposed and how those ideas were responded to. We observed one student, Tia, be positioned and trusted as a source of mathematical authority by their peers and found that Tia had more airtime, made more contributions, and proposed more ideas than their peers. Our theoretical contribution is the link we make between work on mathematical authority and work on epistemic trust by making sense of our findings in terms of research on fact checking and trusting inaccurate informants.