System and method for automatically identifying a source of a run-time error in a computer system comprises a static analysis system (SAS), an instrumentation system (IS) and a post-execution analysis system (PEAS). The is arranged to generate static analysis data on computer program code (CPC) for the computer system, including information on possible behaviors of the CPC when executed. The IS is arranged to instrument the CPC by inserting marker triggers into the CPC that, generate a marker associated with each of a number of predetermined points in the CPC that would be reached during execution of the CPC. Each marker is, uniquely identifiable. The predetermined points are determined in dependence on the static analysis data. The PEASpost execution analysis system is arranged to processes data on a run-time error produced by execution of the instrumented CPC, wherein the generated markers and the static analysis data to identify the source of the run-time error.