I agree very much with ALF, taxonomies like MEDA/ HFACS etc are great ways to classify the findings of an investigation but the danger is the it becomes excuse maker pro. I would suggest a good error investigation course, I did one with Baines Simmons in the UK that was very good. Couple this with a well thought out taxonomy and a system like Safetynet/ AQD or QPulse to manage the information in a sensible way and to track and manage the resulting actions. You're almost a culture change away from a proper SMS.