We demonstrate how the re-marker and reporter facility of the DEWIS e-Assessment system facilitates the capture, analysis and reporting of student errors using two case studies: logarithms and indices for first-year computing students at the University of the West of England, and Sturm-Liouville problems for second-year mathematics students at Leeds University. The differences in approach needed for error capture for commonly used numerical or algebraic answer inputs are discussed and shown to facilitate efficient capture and reporting of student errors. Not only does such information provide a way to tailor question feedback to address these errors for use by future students, but can be made available to current students by re-marking their answers using the newly identified errors and hence making the improved feedback available to them too.