Deciding who investigates
External vs internal workplace investigations: how to choose
An internal investigation suits low-level, straightforward matters where a trained, independent person has the time to do it properly. An external investigator is the safer choice when allegations are serious, could lead to dismissal, involve senior people or HR, or when nobody internal is trained, independent and available. A middle path is to run the investigation internally with external guidance on the allegations, process and report.
External and internal investigations compared
| Factor | Internal investigation | External investigator |
|---|---|---|
| Independence | Risk of actual or perceived bias if the investigator reports to, works closely with, or knows the people involved. | No reporting line or stake in the outcome, which reduces the risk of actual or perceived bias. |
| Expertise | Needs someone experienced and trained in workplace investigations. | Investigations are the investigator’s core work. |
| Capacity | Investigations are time-intensive; the investigator needs significant availability alongside their usual role. | Dedicated time, with a timeframe agreed at the start. |
| Small communities | In regional towns and remote sites, internal investigators often know the people involved outside work. | An outsider can protect confidentiality and credibility. |
| Defensibility | Weaknesses in the process can undermine the outcome if a decision is challenged. | Findings are more likely to withstand scrutiny if a decision is challenged. |
| Best suited to | Low-level, straightforward matters, or informal resolution. | Serious allegations, possible dismissal, senior respondents, conflicts of interest, multiple complainants, whistleblower reports. |
Quick self-check
These five questions come from our guide on when to use an external investigator. If the answer to any of the first three is yes, or to either of the last two is no, an external investigator is worth considering.
The two rules that make an investigation fair
Queensland’s Public Sector Commission guide on workplace investigations describes two core rules of procedural fairness: a person must be given sufficient information to know the case against them and an opportunity to respond (the hearing rule), and a person is entitled to a decision by a disinterested and unbiased decision-maker (the bias rule). Those principles come from public sector administrative law, but they are widely treated as good practice for any workplace investigation. The bias rule is the main reason independence matters. Procedural fairness explained.
What happens if an internal investigation is tested?
If a dismissal is challenged as unfair, the Fair Work Commission must consider matters including whether there was a valid reason related to the employee’s capacity or conduct, whether the employee was notified of that reason, and whether they had an opportunity to respond (Fair Work Act 2009 s 387). In Hatch v WesTrac Pty Ltd [2020] FWC 5729, the Commission found a dismissal unfair after identifying flaws in the employer’s investigation, including that key witnesses were not spoken to and assumptions were not put to the employee for a response.
The middle path: run it yourself, with guidance
Partner with BION Partners to conduct your own workplace investigation. We advise your team on the allegations, process and report so your organisation conducts investigations at acceptable levels of procedural fairness. If your team investigates regularly, the BION Audit reviews your protocol, procedures, documentation and reporting.
Frequently asked questions
Can our HR team investigate a complaint?
Often, yes, if the matter is straightforward and the HR officer is trained, independent of the people involved and has time to do it properly. It is a poor fit where the complaint involves HR, or where the investigator reports to or works closely with the respondent.
Should a manager investigate a complaint about their own team?
Usually not if the complaint is about the manager or their decisions, or if they are close to the people involved. Actual or perceived bias can undermine the findings.
Can we start internally and bring in an external investigator later?
Yes, but it is better to decide early. Clear allegations and terms of reference at the start make any investigation more efficient, whoever runs it. If a matter turns out to be more serious than it first looked, independence becomes more important.
Sources
- Queensland Public Sector Commission: Managing workplace investigations, a practical guide (2024)
- Fair Work Act 2009 (Cth) s 387 (AustLII)
- Hatch v WesTrac Pty Ltd [2020] FWC 5729
Checked 22 October 2026. Laws and guidance change; check the source before relying on it.