Probabilistic evidence graphs can be used to model network intrusion evidence and the underlying dependencies to support network forensic analysis. The graphs provide a means for linking the probabilities associated with different attack paths with the available evidence. However, current work focused on evidence graphs assumes that all the available evidence can be expressed using a single, small evidence graph. This paper presents an algorithm for merging evidence graphs with or without a corresponding attack graph. The application of the algorithm to a file server and database server attack scenario yields an integrated evidence graph that shows the global scope of the attack. The global graph provides a broader context and better understandability than multiple local evidence graphs.