This is a slightly old news, but I co-authored a paper that was recently accepted at Mutation 2016 workshop. The first author, Donghwan Shin (a PhD candidate at KAIST SE Lab), came up with this very neat idea of distinguishing mutants based on the unique sets of test cases that kill them, and subsequently defined a new mutation adequacy criterion that incorporates the diversity of the test cases. Donghwan also has another paper in the main ICST 2016 track, which actually provides the theoretical ground for this new criterion. Congratulations!!!