Julienne: a trace slicer for conditional rewrite theories. Trace slicing is a transformation technique that reduces the size of execution traces for the purpose of program analysis and debugging. Based on the appropriate use of antecedents, trace slicing tracks back reverse dependences and causality along execution traces and then cuts off irrelevant information that does not influence the data observed from the trace. In this paper, we describe the first slicing tool for conditional rewrite theories that can be used to drastically reduce complex, textually-large system computations w.r.t. a user-defined slicing criterion that selects those data that we want to track back from a given point.