Background: The evidence-based approach to policymaking has greatly facilitated policymakers' capacity to make scientifically informed policy decisions, especially in the medical and public health contexts. However, this approach is most beneficial for policy development when trustworthy research is used. Predatory journals and publishers pose a potential threat to evidence-based policy making, since they are more likely than traditional academic journals to publish unreliable evidence. Research Objectives: The purpose of this thesis is to advance knowledge on what factors contribute to the citation of predatory journal articles in policy documents by answering the following research questions: 1) How do people preparing public health documents consider the trustworthiness of research evidence? 2) How do they source and evaluate the research evidence they cite? Methods: I identified a cross-sectional sample of public health policy documents from Overton - the world's largest policy document database - that cited articles published by the OMICS group. OMICS is a well-established predatory publisher. I extracted meta-data (e.g., document source) and document characteristics such as whether they described their method of selection or quality assessment for cited sources. Authors of these documents with contact information listed, as well as a convenience sample of people who have prepared public health documents, were invited for a semi-structured interview. I thematically analyzed these interviews by organizing the codes (both deductive and inductive) into key overarching themes. Results: Two hundred forty-two public health policy documents were included. The World Health Organization was the most common source accounting for 45 documents (19%). A total of 283 articles were cited from 126 OMICS journals. Only 54 (22%) of the policy documents described their source-selection methodology, and 22 (9%) assessed the quality of cited sources. Five key overarching themes were generated from the thematic analysis of the interview data, highlighting that information cited in policy documents is sourced and evaluated in several ways, many of which are related to a series of factors which could be contributing to the predatory journal citations. Conclusion: Public health policy documents are prepared using a variety of methods for information selection and evaluation, but the exact approach for doing so is rarely reported within the document itself. This may contribute to the reliance on untrustworthy research to inform policy; and thus, may help amplify misinformation entering policy globally. Certain steps can be taken to help minimize any potential negative impact of relying on such sources, but a better understanding of policymakers' perspectives may be required to ensure successful implementation.