Our access to human rights violation data has increased with the growing number and size of data collections. We have been combining text-mining and visualization techniques to facilitate big data analysis in human rights research. Taking a user-centered approach, we first surveyed the human rights research literature to understand reported data analysis practices in the field, and then taking a participatory design approach working with oral history researchers to develop a visual analytical tool that facilitates the analysis of collections of audio-video interviews oral history research projects. In this paper we present our current prototype - Clock-based Keyphrase Map (CKM). CKM utilizes Keyphrase technique to identify important topics in the collection and a clock-based visualization to present them in a temporal order. CKM also enables the users to further analyze the collections and share their analysis process with other researchers. We discuss the tool in details including its architecture, the computational and visualization techniques, and the interaction features. Our future plan on evaluation and further development are also discussed in the paper.