While some students successfully navigate normative practices associated with physics instruction, physics educators have argued that many students encounter barriers that lead to undesirable learning outcomes. The reasons for such learning outcomes in physics are multifaceted, with increasing attention being placed on shifting traditional pedagogical practices that limit student participation or promote more factual knowledge over knowledge construction processes. In addition, some active learning practices may also be insufficient for students to leverage personal resources (ideational) and environmental resources (material and relational). By inhibiting epistemic agency, practices that limit the leveraging of such resources have been associated with learning barriers which, we argue, engenders a form of injustice we describe as "Epistemic Injustice". In this paper, we use the framework of Epistemic Injustice to analyze small group interactions in an introductory physics classroom. Through a process we call "Epistemic Resource Negotiation", an episode of video-recorded data of student group work in a Modeling Physics course is examined. In our analysis, we focus on instructional practices to identify epistemic resources and how they are negotiated and accessed in ways that inhibit or afford agency. Our work presents an analytical method that may be used to understand how to move toward more equitable pedagogical practices.