In industries such as the automotive or aerospace, circuits on the field may need monitoring to ensure they fulfill the safety requirements. Return analysis is a bottleneck in semiconductor industry because of the time and costs of extracting the faulty component and sending it back to the manufacturer for an analysis. This can be solved by using self-checking circuits, which offer the possibility of on-line error detection, and can log their errors for later analysis. Errors occurring in a circuit are solved differently depending on their root cause. Because permanent and intermittent faults make it necessary to replace or repair the faulty component, but transients receive a different treatment, it is important to distinguish between these types of faults. The goal of the tool presented in this thesis is the off-line analysis of the faults registered by self-checking circuits in the field.