Incident Investigation
Best Practices

Priorities at the Scene

• Medical attention first - Ensure all injured persons receive appropriate medical care before starting the investigation
• Secure the scene - Prevent further injury and preserve evidence. Use barricades, tape, or personnel to control access
• Document conditions - Photograph the scene immediately from multiple angles before anything is moved or cleaned up
• Identify witnesses - Record names and contact information for everyone present or nearby at the time of the incident
• Notify required parties - Determine if the incident triggers OSHA reporting requirements (8-hour fatality, 24-hour severe injury) or environmental release reporting

Team Composition

The investigation team should include people with different perspectives on the work being performed. A typical team includes:

• Area supervisor or manager familiar with the work process
• EHS professional trained in investigation techniques
• Maintenance or engineering representative (if equipment is involved)
• Frontline employee representative (peer of the affected worker)
• Subject matter experts as needed (chemical engineer, ergonomist, etc.)

Types of Evidence to Collect

• Physical evidence - Equipment condition, broken parts, chemical containers, PPE, environmental samples
• Documentary evidence - Procedures, work orders, training records, maintenance logs, inspection reports, safety data sheets
• Photographic evidence - Scene photos, equipment close-ups, measurements, positions of objects
• Electronic evidence - Security camera footage, data logs, alarm records, access logs
• Witness statements - Written or recorded accounts from people who witnessed or were involved in the event

Interview Best Practices

• Interview witnesses individually, as soon as possible after the event
• Conduct interviews in a private, comfortable setting away from the incident scene
• Begin by explaining that the purpose is to understand what happened, not to assign blame
• Use open-ended questions: "Walk me through what you were doing" rather than "Did you follow the procedure?"
• Let the witness tell their story without interruption, then ask follow-up questions
• Ask about conditions before the incident: Was anything different from normal? Had anything recently changed?
• Document responses accurately and have the witness review the written statement

Effective Corrective Actions

Each root cause identified should have at least one corresponding corrective action. Effective corrective actions are:

• Specific - Clearly defined with a measurable outcome
• Assigned - A single responsible person with authority to implement
• Time-bound - A realistic due date based on complexity and risk
• Prioritized by the hierarchy of controls - Prefer elimination and engineering controls over administrative controls and PPE
• Verified - Not closed until someone confirms the action was completed and is effective

Communication Is Essential

The investigation is not complete until lessons learned are shared with the people who need them. Effective methods include safety alerts or flash reports distributed immediately, toolbox talks and safety meetings, updates to procedures and training materials, and sharing anonymized findings across facilities to prevent similar incidents elsewhere.