What are we really looking for?
Accident investigation aims to answer the three main questions: what happened, why did it happen, and how do we prevent it from happening again in the future. These questions also direct the person conducting the investigation to remain objective, where the overall aim is not to identify whether someone is guilty.
Accidents have multiple causes and underlying contributors. Sticking to the most obvious ones will only tell a part of the story - it is important to look further and deeper. How would it change your mindset if you looked for explanations, instead of causes?
Lessons learned?
Many companies have a well-defined investigation process with good instructions in place. Still, it is common that accident investigations result in vague outcomes. Especially with minor cases with no or very little harm, it is quite common that the accident-preventive measures are extremely simple or focusing only on the most obvious cause.
This highlights the importance of avoiding hasty conclusions and simplifying the outcome of the investigation, for example “…to prevent this from happening again, let’s be more careful.” Although this is a commonly introduced improvement, it has very little or no efficiency in practice.
Preventing it happening again
Instead of focusing (and relying) on human performance only, a better option is to list actions that are targeting both organisational and technical matters. In reference to the example, the outcome should be "...to prevent this from happening again, work practices and risk assessment need to be revised. Also, the adequacy of technical safety in the location has to be ensured, which means new security measures will need to be implemented."
A common issue is that the investigation focuses on merely documenting the case, instead of searching for a more coherent chain of events with causes and consequences. There can be many reasons for this; sometimes there may be lack of time to be allocated for a thorough investigation and reporting.
Also, accidents can be such rare events that no investigation routine has been established for those who conduct each investigation in practice. The overall aim of the investigation can also be unclear. These can lead to outcomes that will not provide much information for effective safety improvements.