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Can a Witness Be Too Good to Be True?: Collusion vs. Inadvertent Contamination in Workplace Investigations

Matt T

Aligned witness accounts—whether among witnesses or with that of a complainant or respondent—can serve as a compelling form of corroborating evidence in workplace investigations. When individuals provide evidence that mirrors or reflects similar details, this consistency is generally viewed as strengthening their credibility and the reliability of the evidence. This may lead an investigator to accept a particular version of events over conflicting or alternative accounts that lack comparable consistency.


However, it is important to consider that it is normal—and even expected—for individuals to recall the same event differently. Memory naturally fades over time, perspectives vary, and minor inconsistencies can even enhance credibility by demonstrating that individual accounts were independently formed. Conversely, when witness accounts mirror each other to an unusual degree, it opens the door to two distinct possibilities: collusion or inadvertent contamination.


  • Collusion occurs when witnesses intentionally coordinate their evidence to influence an investigation, often aiming to appear more consistent and believable. This can involve fabricating details, omitting key information, or tailoring their evidence to create a false sense of credibility.


  • Inadvertent Contamination occurs when witnesses unintentionally influence each other's memory and recall through informal discussions before or during an investigation.


Signs of Collusion or Inadvertent Contamination


  1. Strikingly similar language: When multiple witnesses use the same or very similar terms or phrases, it may suggest they have coordinated their stories. Alternatively, it could indicate inadvertent contamination, where the witnesses have shared details and unknowingly adopted similar language.


  2. Rehearsed evidence: If a witness struggles to recall information naturally or provides overly specific details about certain aspects while being vague about others, it could indicate that the account has been rehearsed. This often occurs when witnesses have worked together to align their stories.


  3. Shifting accounts: If a witness changes their account between interviews, especially when the new version aligns closely with another witness’s version of events, it may suggest that their recollection has been influenced. This is particularly concerning if the witness cannot provide a reasonable explanation for the change in their story.


Addressing Witness Collusion


Evidence of collusion allows for a more focused and direct approach. While the fact that witnesses collude does not necessarily mean that an event did not occur, such behaviour is inherently deceptive. It undermines their credibility, casting doubt on their sincerity and intent. It also significantly compromises the reliability of their evidence and makes it difficult to distinguish between genuine statements and those that may have been fabricated or influenced.


Although evidence of collusion will, in most cases, significantly reduce the weight afforded to the evidence of those involved and may even lead to their evidence being rejected entirely, investigators typically avoid making a formal finding of collusion unless it explicitly falls within their terms of reference. Instead, their role is to thoroughly analyse the evidence, identify indications of collusion, and clearly articulate how such behaviour impacts the credibility and reliability of the accounts in question.


Addressing Inadvertent Contamination


In most workplaces, colleagues frequently share experiences, making inadvertent contamination more common and usually unintentional. This typically occurs through everyday interactions, such as casual conversations or shared discussions, which can unknowingly influence memory and shape how events are recalled. For example:


  • Casual conversations: A casual exchange about “what happened that day” might lead witnesses to adopt similar language or focus on details they heard from others but did not personally observe. Over time, these details can become embedded in their memory as if they were their own observations.


  • Group debriefs or meetings: After an incident, team discussions or informal debriefs can establish a shared narrative among colleagues. This shared narrative may influence individual accounts, as employees may feel compelled to align their recollections with the group consensus, even if their personal experiences differ. These group settings often highlight specific details or interpretations, which can unintentionally override individual memories.


  • Emails or online chats: Witnesses may rely on group emails, messaging threads, or other written communications to refresh their memories about an incident. While this can provide context, it also risks shaping their recollections by introducing details or perspectives they did not observe independently.


  • Shared documentation: Reviewing materials like timelines, incident reports, or summaries prepared by others can also influence witness accounts. If a witness reads a detailed timeline, they may unconsciously adopt certain elements into their own recollection, even if they did not personally observe those details. This can lead to accounts that appear consistent but are unintentionally shaped by shared documentation.


  • Workplace culture or leadership influence: Organisational messaging, leadership briefings, or comments about an incident can significantly affect how employees interpret and recall events. For instance, if a leader emphasises a particular narrative or outcome, witnesses may unconsciously align their accounts to reflect that perspective, believing it aligns with expectations or the “official” version of events.


  • Strong emotional reactions: Emotional conversations with colleagues can amplify certain aspects of an event, creating biases in how those events are remembered. For example, if a colleague expresses strong feelings about a specific detail, others may prioritise or reinterpret their own recollections to match the emotional weight of the discussion. This dynamic can unintentionally align accounts even in the absence of deliberate coordination.


If witnesses have innocently discussed an incident, a more nuanced and thoughtful assessment is required when evaluating their evidence. Such discussions do not inherently undermine a witness's credibility or render their evidence unreliable overall; they may only impact certain aspects.


In terms of credibility, if witnesses are upfront about having had discussions or reviewed documents and maintain transparency in other respects, this openness can support their credibility and rule out collusion. However, careful consideration is still needed to evaluate how those discussions or materials may have influenced the reliability of their evidence.


When assessing reliability, investigators should first evaluate the nature of any discussions that may have influenced the evidence, including who was involved, what was shared, and the level of detail discussed. The reliability of each part of the witness’s evidence should then be assessed independently to determine how these discussions may have shaped specific aspects of their account.


  • Evaluate the impact of discussions: Determine how these conversations may have shaped the witnesses’ accounts, especially in terms of shared details or phrasing.


  • Weigh the evidence carefully: Consider whether the similarities undermine the reliability of specific aspects of the evidence while acknowledging the witnesses’ overall credibility.


  • Maintain neutrality: Treat inadvertent contamination as a natural outcome of workplace dynamics and focus on assessing the reliability of the evidence rather than questioning the witnesses’ motives or intent.


Helpful Questions to Explore


When interviewing a witness, it’s important to ask questions in a neutral and nonjudgmental manner to explore whether their account may have been influenced by external factors without jumping to conclusions. Here are some questions that may assist:


  • Have you spoken to anyone else about the incident?

  • What was discussed, and how in-depth were those conversations?

  • Did you hear or read anything from others that might have influenced your recollection?

  • How confident are you that your account is based solely on your own observations or experiences?


At Riskwise Consulting, our consultants are highly skilled in conducting workplace investigations. If you’re facing a challenging situation, contact us today to discuss how our expertise can help investigate and resolve issues effectively.


Author: RiskWise Director Matt Truelove is a highly experienced investigator and workplace consultant with extensive experience leading complex investigations as a former Detective and Senior Investigator in the Australian Public Service.

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