Incident Investigation Guide | Root Cause Analysis WHS

Why Incident Investigation Matters

Every workplace incident — whether a near miss, injury, dangerous occurrence, or fatality — contains valuable information about weaknesses in your safety systems. The purpose of investigation is not to assign blame, but to understand what happened and why, so that it never happens again.

For businesses across Sydney and NSW, effective incident investigation is both a legal obligation and one of the most powerful tools available for preventing future harm. Under the Work Health and Safety Regulation 2017, PCBUs must investigate notifiable incidents. But best-practice organisations investigate all incidents — including near misses — regardless of regulatory requirements.

As a WHS consultant providing incident investigation services across NSW, Hendricks Australia has investigated incidents ranging from minor first-aid events to fatalities. The methodology we use is consistent regardless of severity: systematic, evidence-based, and focused on systemic improvement rather than individual blame.

What Makes a Good Incident Investigation?

A good incident investigation:

• Starts promptly (ideally within 24 hours while evidence is fresh)
• Is conducted by competent investigators with appropriate training
• Gathers evidence objectively, without prejudging outcomes
• Identifies contributing factors and root causes, not just immediate causes
• Results in corrective actions that address root causes
• Is shared appropriately with relevant stakeholders (workers, management, regulator if required)
• Is followed up to verify that corrective actions have been implemented and are effective

A poor investigation, by contrast, concludes with "worker error" or "failure to follow procedure" and implements a corrective action of "retrain worker" or "remind workers of procedure." These responses do not prevent recurrence — they simply repeat the assumption that the system is fine and the individual is the problem.

The Investigation Process

Step 1: Immediate Response

Following any incident, the immediate priorities are: - Ensure the safety of all persons at the scene - Provide first aid and arrange emergency medical treatment - Notify emergency services if required - Notify SafeWork NSW or the relevant regulator if the incident is notifiable - Preserve the scene and evidence (photographs, samples, equipment) - Record the names of witnesses

Do not disturb the scene before evidence has been secured, unless this is necessary for safety or to provide first aid.

Step 2: Gathering Evidence

Evidence gathering should be comprehensive and objective:

• Photograph the scene from multiple angles
• Collect physical evidence: equipment, materials, substances, PPE
• Review CCTV footage if available (preserve immediately — it may be overwritten)
• Examine relevant documentation: SWMS, risk assessments, training records, maintenance logs, procedures
• Review similar incidents in your organisation and industry
• Check weather conditions, lighting, and other environmental factors

Step 3: Interviewing Witnesses

Witness interviews are critical — people who saw or experienced the incident have information that cannot be obtained any other way. Best practice includes:

• Interview witnesses as soon as possible after the incident
• Interview witnesses individually, not in groups, to avoid group-think and social influence
• Use open-ended questions: "Tell me what you saw" rather than "Did you see X?"
• Record interviews (with consent) or take detailed notes
• Create a non-judgmental environment — witnesses need to feel safe to share what they know
• Interview the injured worker (when they are able) — they often have the most valuable insight

Step 4: Root Cause Analysis

This is the heart of effective incident investigation. Move beyond the immediate cause (what directly caused the incident) to the contributing factors and root causes (why the immediate cause occurred and why the system allowed it to happen).

Useful root cause analysis tools include:

5 Whys: Start with the immediate cause and ask "why" five times. Each answer becomes the next question. This technique often reveals systemic issues that would not be apparent from surface-level investigation.

Fishbone (Ishikawa) Diagram: Categorises contributing factors under headings such as People, Process, Plant/Equipment, Environment, Management System, and External factors. Useful for complex incidents with multiple contributing factors.

Bowtie Analysis: Maps the incident as a "bowtie" with the hazard in the centre, threats (causes) on the left, consequences on the right, and controls on both sides. Useful for identifying control failures.

Step 5: Corrective Actions

Develop SMART corrective actions for each identified root cause: - Specific: Clearly describe what needs to be done - Measurable: Define how you will know it has been done - Achievable: Realistic given available resources - Relevant: Directly addresses the root cause - Time-bound: Has a clear deadline

Apply the hierarchy of controls when selecting corrective actions — prefer elimination and engineering controls over administrative controls and PPE.

Assign each corrective action a responsible person and a due date. Track progress and verify completion.

Reporting Obligations

Notifiable incidents must be reported to SafeWork NSW (or the relevant regulator) immediately. Do not disturb the scene of a notifiable incident without regulator approval (unless required for safety or first aid). Keep records of all notifiable incidents.

Notifiable incidents under the WHS Act include: - Death of a person - Serious injury or illness (as defined in the Act) - Dangerous incidents (as defined in the Act)

Building a Learning Culture Through Investigation

The greatest value of incident investigation comes not from the individual investigation, but from the organisational learning it generates. Share investigation findings and corrective actions with workers — not just the people directly involved. Look for patterns across incidents and near misses. Use investigation data to inform your risk assessments and hazard controls.

Organisations that treat investigation as a genuine learning tool — rather than a compliance exercise or blame mechanism — reduce their incident rates significantly over time.

Hendricks Australia provides professional incident investigation services for organisations that need independent, expert support. Contact our team to discuss your investigation needs.