13 Dos & Don’ts for Assessing Evidence from Incident Investigations


Yes, the goal is to prevent safety incidents from happening. But when an incident occurs despite your best efforts, it’s a learning opportunity. You need to investigate the incident to determine why it happened so you can take appropriate steps to prevent similar incidents from happening in the future. (Failing to learn from safety incidents can be a costly mistake.)

As part of an incident investigation, you’ll gather various kinds of evidence, including witness statements, photos of the scene, pieces of damaged equipment, etc. It’s important that you correctly assess this evidence so that you don’t come to erroneous or incomplete conclusions as to the incident’s cause(s).

WorkSafeBC’s Reference Guide for Employer Incident Investigations recommends that when evaluating the evidence you’ve gathered, consider the following dos and don’ts:


  1. Be objective—don’t start with a fixed opinion
  2. Set out the events in chronological order
  3. Be sure to consider all of the contributing factors
  4. Use a checklist to ensure that you’ve covered all of the areas
  5. Consider what evidence is direct (a witness saw an event happen), circumstantial (indirect evidence, establishing a conclusion by inference from known facts) or hearsay (someone heard something said by someone else).


  1. Draw conclusions on or stop at the first basic cause you find
  2. Believe carelessness is a cause of incidents
  3. Assume contradictory evidence indicates falsehood
  4. Conduct interviews as if in a courtroom
  5. Ask for signed statements from witnesses
  6. Look for only one basic cause
  7. Forget about others’ personal feelings
  8. Overlook the confidentiality of personal medical information.

For more on incident investigations, go to the OHS Insider’s Incident Response Compliance Centre, where you’ll find tools, articles and other information, such as Investigating Workplace Incidents: 9 Common Traps to Avoid and a Model Incident Investigation Form.