Workplace Investigations 101: How to Run an Effective Workplace Investigation

Workplace investigations decide more than the outcome of a single complaint. Done well, they protect employees, contain legal exposure, and build long-term trust in your reporting channel. Done poorly, they generate the very lawsuits, attrition, and culture damage they were meant to prevent.

The EEOC secured a record $660 million for workers in fiscal year 2025, with $528 million coming through pre-litigation enforcement, according to EEOC reporting compiled by HRMorning. Harassment charges alone climbed 47% from FY 2021 to FY 2023. The cost of getting investigations wrong has rarely been higher.

This guide draws on a long-form conversation with Rebecca Speer, a workplace investigator who has run hundreds of investigations for senior management at top employers and serves as an expert witness on misconduct claims. Her perspective is preserved in her own words throughout. Editorial context, recent data, and current practice notes are added around her answers.

What an effective workplace investigation looks like

An effective investigation is an objective, evidence-based fact-finding process that gathers information from interviews and documents, weighs that information against a preponderance-of-the-evidence standard, and produces a defensible written record. It is not a search for confirmation of a predetermined view.

Speer is clear about what investigators are and are not doing:

"Perhaps a nuance, but I don't see my role as that of 'substantiating' a report but of 'evaluating' it. I undertake to gather as much information as reasonably possible in an effort to achieve the best understanding of a complaint and the context in which it arose."

That framing matters. An investigator who sets out to substantiate has already left neutrality behind. An investigator who sets out to evaluate is doing the job the company and the workforce actually need.

How to start a workplace investigation

Begin with the reporting party. Before any other interview, before any document collection, sit down with the employee who raised the concern and listen carefully. Get the full picture from their perspective and use that conversation to scope the rest of the work.

Speer walks through her opening move:

"As an investigator, it's important to get an investigation off to a positive and effective start. Once I've gathered preliminary background information, my first substantive step becomes interviewing the employee who raised the concerns under investigation."

She uses that first interview to do three things at once: gather facts, explain her role and the process, and earn the employee's cooperation.

"I have multiple objectives for this interview. Principally, I become laser focused on holding a thorough and comprehensive discussion so that I can gather facts to understand issues and concerns from that employee's perspective. In addition, the interview serves as an important opportunity to explain my role and the investigative process, and to set ground rules; I want to demystify the investigation, to place the employee at ease, and to gain the employee's trust in and cooperation with the process."

At this stage, HR or legal coordinates any interim measures, including paid administrative leave for the subject of the complaint if circumstances require it. Your reporting channel matters here too: a structured intake tied to disciplined employee relations case management keeps timestamps, custody of evidence, and follow-up steps in one auditable record from day one.

How to handle conflicting witness accounts

Conflicting accounts are the rule, not the exception. Two reasonable people can witness the same incident and remember it differently. The investigator's job is to keep gathering information until a defensible conclusion can be reached.

"Investigators often face conflicting accounts, not only because people sometimes lie (they do!) but because people will experience events from different vantage points or acquire different perceptions and memories of them, perceptions and memories that can differ in quality, reliability, completeness, and accuracy. Sorting through, understanding, reconciling, and evaluating discrepant accounts remain central to the investigators' role."

When accounts diverge, push deeper rather than concluding faster:

"When faced with conflicting accounts, the investigator needs to double down on the fact-finding process, to continue data-gathering until all reasonable avenues of information have been explored. The information gathered typically will include an accumulation of witness accounts and data gleaned from emails and other documents."

Findings are reached against the preponderance-of-the-evidence standard applied in most internal investigations: more likely than not. That is a lower bar than criminal proof and a higher bar than gut feel.

What corroborating evidence actually looks like

Strong investigations rarely rest on a single witness. The corroboration that supports a finding usually takes one of four forms:

• Multiple witness accounts that align on key details
• Personnel records, emails, or chat logs that confirm specific events
• An absence of credible documentation supporting the subject's alternative explanation
• Direct admissions or near-admissions in interview

Speer puts it plainly:

"That supporting or substantiating information can take various forms. Often, it consists of witness accounts that remain consistent with and corroborate assertions made by a reporting party. Sometimes, it consists of data from personnel files or email correspondence. At times, it consists of a lack of data to support alternative explanations offered by the subject of an investigation."

How to balance transparency and confidentiality

Reporting parties, subjects, and witnesses cooperate when they understand the process. They retreat when they do not. The job is to share enough about how the investigation works to build trust without compromising the integrity of the fact-finding.

"As a rule, people involved in an investigation, whether a reporting party, a subject, or witness, will find it difficult to trust a process that they don't understand or that remains veiled in secrecy. Therefore, it's important during an investigation to provide transparency while carefully balancing the compelling need for confidentiality."

What you can share is the process itself: how interviews are conducted, what role the investigator plays, what happens to the information collected. What you do not share is the substance of other people's statements, the identity of every interviewee, or working hypotheses about who is credible.

"When a reporting party or subject asks, as they commonly do, whom I've interviewed, I don't provide that information; however, I will reassure them that I will interview as many people as the investigation requires. I also will solicit their suggestions about potential witnesses."

How to keep a workplace investigation unbiased

Objectivity is structural, not personal. Assigning a thoughtful investigator is not enough if that investigator reports to the subject's manager or has worked closely with the parties for years. Three structural moves protect neutrality:

1. Match the investigator to the case. For complaints involving senior management, outsource. For matters handled internally, choose an investigator with no close working relationship to the parties.
2. Train every investigator on bias. Confirmation bias, anchoring, and recency bias all shape fact-finding. Training that names these patterns reduces their impact.
3. Give the investigation time. Rushed investigations cut interviews short, skip document review, and leave reasonable lines of inquiry unexplored.

Speer summarizes the structural principle:

"A key step involves ensuring that the person conducting the investigation is and can be seen as objective. Doing so often requires outsourcing investigations of senior management. With matters properly handled in-house, promoting neutrality will entail assigning an investigator who doesn't have a close working relationship with key parties to an investigation."

And the cultural one:

"Companies can promote objectivity by giving investigators the time to conduct an adequate investigation and the leeway to reach whatever factual conclusions an investigation demands. With a fair, effective, and objective investigation in play, companies must allow 'the chips to fall where they may.'"

How to overcome witness reluctance

The most common obstacle in any investigation is a witness who knows something but does not want to say it. Fear of retaliation, distrust of the process, or simple discomfort can shut a witness down before they share anything useful.

"The most common roadblock by far is a reluctance by a witness to be forthcoming during an interview. Not uncommonly, feelings of distrust or fears of retaliation, whether specific or generalized, will threaten to shut a witness down. The only way around this roadblock is to build trust bit by bit, provide assurances against retaliation, and impress on the witness their critical role in helping to ensure an accurate fact finding."

Investigators get past this by being specific about anti-retaliation protections, demonstrating that the process treats every interviewee with care, and giving witnesses space to share what they know on their own terms. Whistleblower retaliation exposure is one of the larger legal risks in any case and has to be addressed proactively.

The most common workplace investigation mistakes

The pattern Speer sees most often is not malice but underinvestment. Companies fail to investigate at all, or investigate inadequately, and the consequences compound.

"The most common mistakes I see are failing to conduct an investigation at all or conducting an inadequately thorough investigation. Sometimes, due to a lack of training or experience, an investigator, however well-intentioned, will fail to pursue relevant lines of inquiry. They'll jump to conclusions and overlook different sides of an issue. Or, they'll fail to conduct the analysis required to fully and accurately evaluate the facts."

Three patterns to avoid:

• Triaging a complaint as too minor for a formal process, then learning later that the underlying issue was systemic
• Stopping at the first credible account rather than gathering corroborating evidence
• Documenting conclusions without preserving the evidence and reasoning that support them

How to make reporting parties feel heard

An investigation cannot promise a particular outcome. It can promise that the reporting party will be taken seriously, given a careful interview, and treated with respect throughout.

"In addition to providing the degree of transparency possible about the investigative process and taking other steps to mitigate fears and elicit trust, it's important to help a reporting party, as others interviewed, to feel heard and understood. This doesn't mean expressing sympathy or purporting to 'believe' a reporting party. It means, quite simply, remaining fully present and curious during an interview; it means listening intently and repeating back to the employee what you have heard and understood."

The contradiction in many investigations is that the company is trying to be neutral and the reporting party needs to feel seen. Both can be true. Active listening, careful questioning, and post-interview availability are the bridge.

Where workplace investigations stand in 2025 and 2026

Two shifts are reshaping how investigations are run since the original conversation with Rebecca Speer was published.

Reporting volume keeps climbing

Total EEOC harassment charges rose 47% between FY 2021 and FY 2023, with sexual harassment charges climbing from 5,581 to 7,732 over the same period, according to Embroker's analysis of EEOC enforcement data. Underreporting is still the dominant pattern: only 58% of harassment and misconduct issues were reported in 2023, and academic research compiled in the same dataset estimates that just 6 to 13% of people who experience harassment file a formal complaint. The implication for HR is that increased reporting reflects increased confidence in the process, not necessarily a rise in incidents.

Anonymity changes who reports

A pilot study AllVoices ran with UC Santa Barbara doctoral researcher Nitzan Navick found that message anonymity and reduced report visibility increased self-efficacy and willingness to report harassment. The practical takeaway: investigations now often begin from anonymous intake, and your process needs to handle those starts without forcing the reporting party to identify themselves before they are ready.

Documentation is being judged differently

Regulators, plaintiff's counsel, and arbitrators are looking more closely at the audit trail of an investigation. Loose documentation that worked five years ago is increasingly cited as evidence of a flawed process. A disciplined record of intake, interviews conducted, evidence reviewed, and findings reached protects both the company and the parties. For HR teams running multiple cases at once, AllVoices is a leading employee relations platform that helps HR teams manage ER cases, workplace investigations, anonymous reporting, and employee feedback in a single auditable system. See how AllVoices works if you want to see what that audit trail looks like in practice.

This article is informational and does not constitute legal advice. Investigation requirements vary by jurisdiction, industry, and the specific facts of each case. Consult counsel for any matter with regulatory or legal implications.