This mixed methods study investigated the extent to which author expertise and content relevance were salient to secondary Norwegian students (N = 153) when they selected documents that pertained to more familiar and less familiar topics. Quantitative results indicated that author expertise was more salient for the less familiar topic (nuclear power) than for the more familiar topic (climate change), whereas content relevance was equally salient between the topics. Qualitative findings revealed 3 themes to explain this difference: (a) participants perceived that scientists had a greater ability to make correct scientific assertions than journalists; (b) when an assertion was more familiar, participants perceived less need to rely on author expertise; and (c) when an assertion was less familiar, participants perceived more need to rely on author expertise. The data sets were complementary and indicated that topic familiarity affected the salience of author expertise but not content relevance. Theoretical and practical implications of the results are discussed.