You can actually learn a lot from a candidate's past projects if you know how to follow up with the right questions. Someone who had a negative net contribution

You can actually learn a lot from a candidate's past projects if you know how to follow up with the right questions. Someone who had a negative net contribution on a project will not have anything interesting to say about the data structures or algorithms they used. They won't have interesting war stories to share either (e.g. nasty bug fix, conflict with management or team and how they overcame it, etc.).