Incident investigation: build an explanation from supported facts
After a ladder incident on a townhouse project, the first message says the worker rushed. Nobody has yet checked which ladder was available, what instruction was received or how the task changed.
An early explanation can become the official story before the team has examined the work. Keep observations, recollections and hypotheses separate. The responsible investigation should examine the conditions that made the event possible, not simply repeat the first description of someone’s behaviour. Use the actual required investigation process, competent roles and reporting rules; this lesson supplies a practical evidence structure, not a legal investigation timetable.
Test the explanation against the evidence
- Define the investigation boundary. Establish the event, affected task, location and period being examined. Confirm the responsible investigators and any regulator or scene directions before collecting material. Record the questions still open. A useful opening question is specific: which equipment and information were available for this task? It is not a conclusion that the person chose badly.
- Build a timeline with visible sources. Record relevant instructions, task changes, equipment availability, observations and responses in order. Label whether an entry comes from a dated document, direct observation or later recollection. Preserve originals through the appropriate process. If two accounts disagree, show the difference and seek clarification instead of quietly replacing one with the more convenient version.
- Examine conditions behind the immediate event. Ask about planning, task suitability, training, supervision, resources and conflicting instructions where relevant. OSHA’s overview describes investigation beyond fault to underlying causes. Use that principle without copying a generic cause into the finding. A missing instruction is a question to examine; it is not automatically the proven cause of this particular incident.
- Connect findings to specific actions and checks. Give each supported finding an appropriate action, responsible person and verification method through the competent review. Identify unresolved evidence and any interim protection. A toolbox reminder may be appropriate communication, but it cannot replace a needed equipment, method or planning change. Review whether the action addresses the finding and whether it was actually implemented.
Common mistakes
- Turning a witness’s explanation into an established fact.
- Selecting corrective actions before the findings are supported.
- Closing a technical control gap with attendance at a briefing alone.
Checklist
Make the investigation traceable
- Actual event and responsible process.
- Timeline entries linked to their sources.
- Assumptions and conflicting accounts visible.
- Findings connected to appropriate actions.
- Implementation and effectiveness checked.
Check your understanding
A witness says the worker rushed. Is that enough to close the investigation with a reminder to slow down?
