Much research has been conducted in the past decade and a half on the effectiveness of Laboratory for Innovative Technology and Engineering Education (LITEE) Case Studies in engineering education. A case study, as defined in this study context, is an online, multimedia tool designed to bring real-world problems into the classroom. Much past and current data from the Lab and other researchers have come from survey or focus group research, often measuring student performance or perceptions of performance while using the case studies. What researchers have not yet examined is how students actually interact with the case studies, and how this interaction encourages student learning. This paper uses a framework from the field of communication to examine this phenomenon. Using Spinnuzi's framework of the "genre ecology," the paper explains how case studies enable compound mediation, which in turn enables student learning. (Contains 6 figures.)