We have designed a system to support collaborative legal case rea-soning and building. The design is based on our understanding of the corporate litigation domain acquired through analysis of the literature, interviews of vari-ous parties involved in corporate litigation processes, and studies of the com-mercial tools already available. In this paper we illustrate the designed system and in particular the interaction modes that it supports that we believe address a number of the requirements that emerged through our analysis. We also de-scribe its main components and their integration, including a knowledge model that represents the domain, and a natural language processing component for extracting semantic information. A description of a prototype system is also provided.