Three Staff Under Investigation: Two Cleared, One Guilty
£23,000 in high-value electronics stock had gone missing from a distribution centre over six months. An internal audit narrowed 11 suspects to 3. All three were tested with P300 EEG in a single day. Two returned clear results and were exonerated with written documentation. One returned deception-indicated. The right person was identified.
Important Use & Limitations Notice
Anonymisation: All names, company details, and identifying information have been anonymised or adapted. This case study is presented as a documented investigation outcome for educational purposes.
Evidential use: P300 EEG results in this case were used as supporting evidence in an internal HR disciplinary process and subsequent employment proceedings. Not presented as standalone determinative evidence.
Purpose: For educational and investigative planning purposes only. Not legal advice.
Case Background
Between August 2024 and January 2025, a West Midlands distribution centre supplying electronics to UK retailers identified a recurring discrepancy between goods received and goods dispatched from a high-value secure pick zone. Stock counts confirmed that £23,000 in items — predominantly compact audio equipment and accessories — had been removed outside of any authorised order or write-off process.
The secure pick zone had access controlled by key fob. Audit logs identified 11 staff members who had made unscheduled access to the zone during the loss period. CCTV coverage of the zone had a known blind spot, and footage from adjacent areas provided movement data but no direct evidence of removal. The operations manager and HR director had conducted initial interviews with all 11 staff — none had made admissions, and the verbal accounts were broadly consistent.
An external loss prevention consultant reviewed the audit logs, shift patterns, access frequency data, and interview notes. The review narrowed the likely suspects to three individuals whose access patterns, shift timing, and post-interview behaviour were most consistent with the loss profile. The company instructed P300 EEG investigation of all three before any disciplinary action was taken.
How the investigation reached three suspects
Why the investigation had stalled at three suspects
- No admissions: All three had denied involvement across multiple rounds of informal questioning. Their accounts were internally consistent and did not contradict each other in ways that could be exploited.
- Equal evidential weight: The access log and shift data pointed at all three roughly equally. The loss prevention consultant could not rank the three suspects by probability of guilt on the basis of the available data alone.
- Tribunal risk: Disciplining or dismissing any of the three without a stronger evidential basis risked wrongful dismissal claims from innocent staff. The company's HR advisers were clear that acting on suspicion alone was not an option.
- Workforce impact: The investigation had been running for three months. The entire team of 11 was aware of it. Morale had deteriorated and two members of staff had submitted grievances about the conduct of the investigation. The company needed a resolution that was both fast and defensibly fair.
Investigation Design
All three subjects were tested on the same day in sequential sessions, each isolated from the others before and during their appointment. The probe design was identical for all three — built around specific details of the thefts that only the person responsible would have stored in neurological memory.
Probe design — what only the thief would know
The probe stimuli were built around four categories of specific knowledge:
- Item-specific knowledge: The precise stock keeping units (SKUs) and product descriptions of the items taken — details available on the warehouse management system but not known from memory by most staff.
- Method of removal: The specific route and timing patterns used to remove items from the zone without triggering the access log at the monitored exit. This information had been reconstructed by the loss prevention consultant from the audit data and was not publicly known within the workforce.
- Concealment and disposal: Specific details about what happened to the items after removal — details that only someone who had handled the stolen stock after the act would hold in memory.
- Financial specifics: The approximate total value of goods removed in the final month of the loss period — a figure known internally to the investigation team but not disclosed to any of the 11 staff under suspicion.
Subject A — Session 1, morning
90-minute session including 15-minute pre-test briefing and baseline calibration. Three probe sets covering item-specific knowledge, removal method, and financial specifics. Verbal result delivered to HR director at session close.
Subject B — Session 2, midday
90-minute session following same structure. Subject B had not been in the building during Subject A's session. Same probe sets delivered in independently randomised stimulus sequences to prevent any cross-contamination of results.
Subject C — Session 3, afternoon
90-minute session. Subject C arrived after Subject B had left the building. Same probe structure. Fourth probe set added covering a specific concealment detail that the loss prevention consultant had identified as highly discriminating between genuine innocence and involvement.
Verbal results delivered — end of day
Results for all three subjects delivered to the HR director and operations manager in a single debrief at the close of the afternoon session. Written reports for all three subjects delivered the following morning.
Results
Subject A
Produced no meaningful P300 recognition responses to any probe set. Brain responses were consistent across all stimuli with no differential pattern between probe and filler items. Clear result on all three probe sets. Exonerated.
Subject B
Produced no meaningful P300 recognition responses across all three probe sets. Baseline was well-defined and consistent. No recognition signatures for any of the specific theft-related stimuli. Clear result. Exonerated.
Subject C
Produced statistically significant P300 recognition responses across all four probe sets — probability scores of 91%, 94%, 89%, and 97% respectively. Strongest responses on the concealment/disposal probe and the financial specifics probe. Deception indicated.
The two clear results were not a consolation prize — they were a core deliverable
Subject A had been the most strongly suspected individual going into the investigation, based on the access frequency data. Subject B was a team leader whose involvement, if confirmed, would have had the most serious organisational consequences. Both were returned clear. Both received written documentation of their P300 EEG result.
For Subject A in particular — who had been under the heaviest suspicion for three months — the written clear result provided objective, documented, neurological evidence of innocence that no interview, character reference, or verbal assurance could have matched. It ended his involvement in the investigation definitively, on factual grounds rather than on the balance of HR judgment.
Why P300 EEG discriminates accurately where interviews cannot
Detection Method Comparison — Multi-Suspect Workplace Investigation
P300 EEG
Tests whether each subject's brain holds specific knowledge of the theft. An innocent person's brain cannot recognise probe stimuli relating to acts they did not commit — regardless of how suspicious their access patterns appear. Two clear results from three suspects is not a failure rate. It is the technology working exactly as intended.
HR Interview Process
Six rounds of interviews across 11 staff had produced no admissions and no new evidence. Experienced HR investigators cannot reliably distinguish deceptive from truthful denial at a level that meets the disciplinary evidence threshold. The interview process correctly identified that something was wrong — it could not identify who was responsible.
Key Investigation Findings
- Subject C produced deception-indicated results on all four probe sets, with his strongest recognition responses on the concealment/disposal probe (97%) — suggesting he held detailed memory of what happened to the stolen items after removal, not just the act of removal itself.
- Subject A — the most strongly suspected individual based on access data — was returned clear across all three probe sets. His exoneration prevented a wrongful dismissal of a four-year employee that would have carried significant tribunal risk.
- Subject B — a team leader whose involvement would have had the most serious organisational consequences — was also returned clear, allowing the investigation to proceed against Subject C without the reputational and structural damage that a team leader dismissal would have caused.
- All three subjects were tested, results were delivered, and the HR process could proceed — within a single working day. The three-month stalled investigation was resolved before the end of business on the day of testing.
- The two clear results, documented in written reports, were communicated to both cleared subjects the following morning — providing them with objective evidence of exoneration before any disciplinary action against Subject C was announced to the team.
Investigation Outcome
Disciplinary process — Subject C
Subject C was invited to a formal disciplinary hearing with the P300 EEG report provided as part of the evidence pack. During the hearing he was given the opportunity to respond to the report. He provided no explanation for the specific recognition responses documented across all four probe sets. Following the hearing, he was dismissed for gross misconduct — theft.
Employment proceedings
Subject C submitted an employment tribunal claim for unfair dismissal. The company's legal team presented the full evidential package at the preliminary hearing — the audit log analysis, the loss prevention consultant's report, and the P300 EEG written report. The tribunal noted the combination of documentary evidence and the objective neurological assessment. The claim was dismissed at the preliminary stage.
Civil recovery
The company initiated civil recovery proceedings against Subject C for the £23,000 in stolen stock. The proceedings were settled before a full hearing, with a partial recovery agreed. The P300 EEG report featured in the particulars of claim as documented evidence of concealed knowledge of the full scope of the theft.
Team communication and morale
The two cleared subjects were notified of their exoneration by the HR director on the morning after the investigation. The result — that two of the three tested staff were confirmed innocent and one guilty party had been identified — was communicated to the broader team as part of the investigation close-out. The company's HR adviser subsequently reported that the two grievances submitted during the investigation were withdrawn within a week of the outcome being communicated.
What This Case Demonstrates
Accurate discrimination is the point — not universal accusation
The most common concern employers have about lie detection in workplace investigations is the fear of false positives — of the technology returning everyone as guilty, or of it being used to reach a predetermined conclusion. This case directly addresses that concern. Two of three subjects were returned clear. The most strongly suspected individual on the basis of circumstantial evidence was one of the two cleared. P300 EEG does not find people guilty. It finds out who holds the specific knowledge that only a guilty person would have.
Written exoneration has operational value beyond the investigation
The two cleared subjects did not merely walk away uninvestigated. They left with written P300 EEG reports documenting that their brains produced no recognition responses to specific details of a theft they had been suspected of for three months. That documentation has value that extends beyond the investigation: it protects the employer against wrongful dismissal risk, it protects the cleared employees against future recurrence of the suspicion, and it demonstrates to the wider workforce that the investigation was conducted with a commitment to factual accuracy rather than a presumption of guilt.
Speed resolves workforce damage that prolonged investigations cause
Three months of unresolved investigation had produced two staff grievances, measurable morale deterioration, and reputational damage to a team leader whose innocence was only documented on the day of testing. A P300 EEG investigation commissioned at the point when the suspect pool had been narrowed to three would have resolved the matter in a single day — at a fraction of the management time, legal cost, and workforce disruption that the extended process had generated.
Investigating Workplace Theft or Misconduct?
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