Incident Investigation
Core concepts
An incident is an undesired event that harmed or could have harmed people, property, or the environment; a near miss is an incident without actual harm. Investigation seeks facts, not blame: secure the scene, preserve evidence, interview witnesses promptly and separately, document conditions, and establish a timeline. Causal analysis moves from immediate causes (unsafe acts or conditions) to root causes (management-system weaknesses such as inadequate design, training, maintenance, or change management). Methods include 5 Whys, fishbone diagrams, fault trees, and barrier analysis. Corrective actions should be specific, assigned, tracked, and verified. Reporting and recordkeeping requirements may differ from internal investigation thresholds. A just culture encourages reporting while maintaining accountability.
Traps
- Stopping at “worker carelessness” without asking why the system allowed the error.
- Assuming one root cause; most incidents have multiple contributing factors.
- Interviewing witnesses together or leading them toward a preferred conclusion.
- Treating near misses as unimportant; they are free lessons.
- Writing corrective actions that cannot be verified.
Worked example
A worker slips on an oily floor. Immediate cause: oil on the floor. Deeper causes: a leaking machine, no scheduled inspection, and no absorbent supplies nearby. Corrective actions: repair the leak, add leak inspection to the maintenance route, and place spill kits at the line. Rule of thumb: ask “why” until the answer points to a system you can change, then verify the change.