Investigating incidents
Find the cause, not the culprit
An investigation has one purpose: to establish what happened and why, so that it does not happen again. It is not a disciplinary process and it is not about apportioning blame. Blame-driven investigation destroys the reporting culture that supplies the evidence.
A practical sequence: make the area safe and secure the scene; preserve evidence (equipment, substances, CCTV, photographs, documents such as training and maintenance records); gather information from witnesses promptly and separately, listening rather than leading; establish the sequence of events; identify immediate causes (the act or condition that triggered the event) and then root causes (the underlying management factors - design, procurement, training, supervision, maintenance, planning). Then recommend actions with owners and dates, report the findings, and follow up to confirm the actions were done.
Useful tools are the five whys (keep asking why until you reach something you can fix at management level), fishbone or cause-and-effect diagrams, fault trees, and simple timelines.
'Carelessness' is an unusable conclusion. Underneath almost every unsafe act there is an unsafe condition or a management decision that made the behaviour likely. Serious incidents, specified injuries, dangerous occurrences and certain diseases must be reported to the enforcing authority under RIDDOR.
Traps: stopping at the immediate cause; investigating only injuries and ignoring near misses; delaying witness interviews; recommending 'retrain the operator' as the sole action; treating the investigation as a hunt for someone to punish.
Rule of thumb: keep asking 'why' until the answer is a system failure someone can actually fix.