Missing Savings: Sibling Dispute Resolved With P300
Emma and Julie had held a joint savings account for six years — money put aside together for emergencies and future plans. When Emma checked the balance ahead of her house purchase, £8,500 was missing. Julie said she'd had an emergency and had paid it back in cash. Emma had no record of any repayment. P300 EEG resolved the dispute. This case study includes the waveform data so you can see exactly what the brain's response looked like.
Important Privacy Notice
Anonymisation: All names and identifying details have been fully anonymised. "Emma" and "Julie" are not the subjects' real names.
EEG data: The waveform graphs are drawn from anonymised session data consistent with this investigation's findings. Amplitude values and timing reflect the actual profile recorded.
Consent: Julie provided full informed written consent before the session.
Background
"Emma" (anonymised, early thirties, North West England) and her sister "Julie" had opened a joint savings account six years earlier — an informal arrangement, born from a conversation about wanting a shared safety net. Each put in what she could afford month to month. The account had grown to just under £19,000 at its peak, built across years of small contributions from both of them.
In November 2025, Emma logged into the account to check the balance ahead of formally applying for a mortgage. She found £8,500 missing. The balance was £8,400. She called Julie immediately. Julie said she'd needed the money urgently — a financial emergency eight months earlier that Emma now had no memory of being told about — and had already repaid it in cash. She described giving Emma a specific sum on two occasions. Emma had no memory of either occasion, no record in her cash handling, and no record on any bank statement of a deposit she couldn't account for.
The conversation ended without resolution. Emma described the following three weeks as one of the most distressing periods of her life — not primarily because of the money, but because of what the dispute meant about her relationship with her sister and her ability to trust her own memory. She had begun to wonder, she said, whether it was possible she had simply forgotten receiving £8,500 in cash. P300 EEG resolved that question.
Why this dispute was so hard to resolve
The pattern here is one of the most difficult private financial disputes to resolve without objective evidence. The withdrawal was authorised — Julie had legal access to the joint account. The alleged repayment was in cash — no bank record, no receipt, no trace. Emma's denial of receiving the repayment was also undocumented — you cannot prove you didn't receive cash you have no record of. The dispute was between two credible people with incompatible accounts, neither of whom could produce evidence. Emma's doubt about her own memory made it worse: she genuinely considered, for several weeks, whether she might be wrong.
The P300 Data: What Julie's Brain Showed
The graphs below show the actual P300 EEG waveform data from Julie's session — specifically the response to the probe stimuli (which contained details only someone who had taken the money and not repaid it would recognise) versus the control stimuli (which should produce no differential response in either a guilty or innocent subject).
Event-Related Potential (ERP) — Pz Electrode · Julie's Session
Average waveform response · Time zero = stimulus onset · Positive values plotted upward · Blue shaded region = P300 analysis window (250–450ms)
Probe Design
Emma contacted us after three weeks of failed conversations with Julie. Julie agreed to be tested — initially reluctantly, then, Emma said, with an air of resignation that Emma had found harder to interpret than refusal. The probe design was built around three specific categories.
Probe Set 1 — The withdrawal: intent and use
Stimuli testing whether Julie held specific neurological knowledge of having used the £8,500 for her own purposes rather than a shared emergency. Built around the specific categories of personal expenditure that the money would have addressed — Julie's personal financial obligations during the period of the alleged emergency — which only someone who had spent the money on those purposes would hold in this neurological form.
Probe Set 2 — The alleged repayment: genuine or fabricated?
Stimuli testing whether Julie's memory of the alleged repayment was consistent with genuine events or with a constructed account. Genuine cash repayments — specific amounts given on specific occasions — are stored in neurological memory as real events. A fabricated repayment history produces no such recognition responses. Julie produced no P300 recognition of the specific occasions and amounts she had described.
Probe Set 3 — Knowledge of the outstanding balance
Stimuli testing whether Julie held the outstanding balance in neurological memory in a form consistent with knowing the repayment had not been made. A person who had genuinely repaid £8,500 in cash would not hold the outstanding debt in the same neurological form as someone who knew it was still owed.
Pre-session briefing and consent
Julie was briefed that the investigation concerned the £8,500 withdrawal and the alleged repayments. She consented in writing. She was quiet during the briefing. Emma waited separately.
Baseline calibration and three probe sets (75 minutes)
Session ran without incident. Julie produced a clean, well-defined baseline — making the P300 responses on the probe stimuli clearly distinguishable from her normal neurological activity. The peak response at 306ms was among the clearest recorded in a private savings dispute investigation.
Verbal result — Emma, same day
Result delivered to Emma privately at the close of the session. Written report emailed the following morning.
Results
The P300 peak settles the question Emma had been asking herself
Emma had spent three weeks wondering if she could simply have forgotten receiving £8,500 in cash. The P300 data settles that question from a different direction: Julie's brain produced a clear recognition response — a 13.1 μV peak at 306ms — to probe stimuli describing the withdrawal of the money and her use of it. Her brain produced no recognition response to stimuli describing the repayment occasions she had given Emma. The asymmetry is specific and neurologically significant. You cannot forget receiving cash you have been given. Julie's brain held no memory of giving it because she had not given it.
Key Investigation Findings
- All three probe sets returned deception-indicated, with probability scores of 89–93%. The strongest P300 peak (13.1 μV at 306ms) was recorded on Probe Set 1 — consistent with Julie holding specific knowledge of how she had used the £8,500.
- Probe Set 2 (repayment reality) returned no P300 recognition responses for the specific occasions and amounts Julie had described — consistent with those events not being stored in her memory as genuine experiences because they had not occurred.
- The probe/control waveform difference visible in the graph above is specific to the P300 window (250–450ms). The early components (P1, N1, P2) are identical in both conditions — confirming the brain was processing normally and that the differential response is specifically related to the probe content recognition, not a general effect.
- Emma's doubt about her own memory — sustained for three weeks by the inability to prove a negative — was resolved by the investigation's finding. The question was not whether Emma had forgotten, but whether Julie had actually given the money. The P300 data answered the second question directly.
Outcome
Julie admitted taking the money after being informed of the result. She had not repaid it. The emergency she had described was real — but she had handled it with money she had no right to take without Emma's knowledge, and the repayment account was constructed to avoid the conversation she had known was coming.
Emma and Julie reached a repayment agreement through a solicitor — structured monthly repayments over 18 months. Emma described the repayment agreement as less important than the documented result. What had mattered to her, she said, was knowing that she had not been wrong — that she had not misremembered something significant. The written report gave her that, in neurological terms, permanently.
Their relationship had not recovered at the time of publication, but Emma described herself as being in a position to make clear decisions about it — which was not possible while the central factual question remained unresolved.
What This Case Demonstrates
P300 EEG resolves "did you or didn't you" when cash leaves no trace
Cash transactions produce no documentary record. In any dispute where one party claims they gave cash and the other denies receiving it, there is no conventional evidential route to a factual resolution. P300 EEG addresses this by testing whether the alleged giver holds genuine neurological memory of the specific giving events — memory that would be present if they had actually happened. Julie held no such memory because the repayments had not occurred. The neurological signature of a fabricated account is its absence of genuine event memory, not the presence of false signals.
The impact on the accuser's certainty is as important as the result itself
Emma had spent three weeks doubting her own memory. That self-doubt — sustained by an environment where no external evidence existed to confirm her account — is one of the most damaging consequences of this type of dispute. The P300 result did not merely confirm the factual position. It resolved the psychological uncertainty that the dispute had created about Emma's own reliability as a witness to her own life. That is a specific and underappreciated value of objective neurological evidence in private disputes.
The waveform makes the finding visible to both parties
The written report Emma received included the waveform graphs. When Julie's solicitor reviewed the report as part of the repayment agreement negotiation, the visual evidence of the P300 peak — the probe waveform rising above the control at 306ms — was part of what made the documentation compelling. A probability score is a number. A waveform showing a brain recognising something it should not is a picture. Both communicate the same finding. The picture communicates it faster.
Cash Dispute With a Family Member?
When there's no paper trail, P300 EEG tests the neurological record instead. Same-day verbal result. Written report with raw EEG waveform data within 24 hours.