Adverse Event: Investigations

Once an employer has been notified of an adverse event and been given basic information on what happened, they must decide whether it should be investigated and to what depth.

The extent of the investigation should be determined by the potential consequences of the event and the likelihood of it recurring, and not just on the nature of a near miss, injury or ill health that might have occurred.

The decision to investigate can be determined by relating the worst potential consequence of the adverse event with the likelihood of its recurrence.




1. In a minimal level investigation, the relevant supervisor will look into the circumstances of the event and try to learn any lessons which will prevent future occurrences.
2. A low level investigation will involve a short investigation by the relevant supervisor or line manager into the circumstances and immediate, underlying and root causes of the adverse event, to try to prevent a recurrence and to learn any general lessons.
3. A medium level investigation will involve a more detailed investigation by the relevant supervisor or line manager, the health and safety adviser and employee representatives and will look for the immediate, underlying and root causes.
4. A high level investigation will involve a team-based investigation, involving supervisors or line managers, health and safety advisers and employee representatives. It will be carried out under the supervision of senior management or directors and will look for the immediate, underlying, and root causes.

(HSE (2004) ‘Investigating accidents and incidents', HSG245, pp.8, 13 https://www.hse.gov.uk/pubns/hsg245.pdf)