The incident investigation should basically answer the following six key questions

a.    Who 

• was injured?
• saw the incident? (Injury)
• was working with him/her?
• had instructed, trained, assigned the affected person/
• else was involved?
• Can help prevent the re-occurrence?
  

b.    What 

• was the incident?
• was the injury/illness?
• was being done at time of injury or incident?
• were they told to do so?
• tools were being used?
• machinery was involved?
• operation was being performed?
• instruction had been given?
• precautions were given?
• precautions were necessary?
• PPE was used or should have been used?
• did other do to contribute to the incident?
• problems or questions was encountered?
• did the employee and others do after the incident?
• did witnesses see?
• will be done to prevent re-occurrences.
• safety rules or procedures were violated?
• safety rules or procedures were lacking?
• safety rules or procedures were needed?
• additional training should be included?
  

c.    When 

• did the injury or incident occur?
• did the employee begin the task?
• was the employee assigned to the task?
• were the hazard or risk pointed out to the employee?
• did the supervisor last check on the employee’s progress?
• did the employee last notice that something is wrong?
• was appropriate training provided?
• was a risk assessment done?

d.    Why 

• was the employee injured?
• did the employee behave that way?
• did other persons behave that way?
• was PPE not used?
• were specific instructions not given to the employee?
• was the employee in that position/place?
• was the employee using that machine or tool(s)?
• did the employee not check with the supervisor?
• did the employee continue working under the circumstance?
• was the employee allowed to continue working?
• wasn’t the supervisor there at the time?
  

e.    Where 

• did the injury or incident occur?
• was the employee at the time of the incident?
• was the supervisor at the time of the incident?
• were co-workers at the time of the incident?
• were other persons involved at the time?
• were the witnesses when the incident occurred?
• else does this or a similar condition exist?
  

f.     How 

• was the employee injured?
• could the injury/illness have been avoided?
• could co-workers avoid similar injury/illness?
• could the supervisor have prevented the injury/illness?