Forensic Credibility Assessment for Alleged Victims of Sexual Abuse and Violence
Integrated forensic credibility assessment
A structured forensic credibility assessment integrating statement analysis, psychophysiological examination and Bayesian analysis to evaluate the credibility and consistency of examined accounts in cases involving alleged victims of sexual abuse or violence.
The Centre for Forensic Neuroscience may consider forensic credibility assessments in carefully selected cases involving alleged victims of sexual abuse or violence. The polygraph examination is one component of a broader assessment that integrates multiple sources of information to produce a structured forensic opinion on the credibility and consistency of a specific disclosure, account or written statement.
Service scope: This service is currently offered only to alleged victims of sexual abuse or violence. It is not offered to alleged perpetrators, nor is it intended to determine guilt or innocence.
A Carefully Limited Investigative Role
The examination is not a substitute for police, legal, clinical or safeguarding processes. It is a supplementary investigative process that depends on suitability screening, informed consent, safeguarding review and professional judgement.
"A forensic credibility assessment does not determine whether abuse occurred and should not be treated as proof of any alleged event."
A favourable examination outcome does not verify an allegation, and an unfavourable outcome does not invalidate an allegation.
When This Service May Be Appropriate
Specific, voluntary and professionally screened
The Centre for Forensic Neuroscience only considers this service where the referral question can be clearly defined and the result will be interpreted alongside other evidence and professional advice.
Specific Disclosure
A specific disclosure, account or written statement may benefit from additional investigative assessment.
Voluntary Consent
The person is participating voluntarily, with informed consent and without coercion or pressure.
Safeguarding Review
There are no safeguarding, welfare or trauma-related concerns that would make testing inappropriate.
Supporting Evidence
Any opinion will be considered alongside witness, documentary, digital, clinical, safeguarding and legal material.
Defined Referral Question
The referral question can be clearly defined before any examination is accepted.
What the Assessment Evaluates
The assessment is structured around a defined account, disclosure or written statement. It evaluates whether the examinee maintains the credibility and accuracy of a specific account, whether a written statement is consistent with the examinee's account, whether significant physiological responses occur in relation to carefully structured relevant questions, and whether the account remains consistent during structured examination.
The assessment is not designed to determine whether abuse occurred. It evaluates the credibility and consistency of the examined account within a defined and carefully limited scope.
How Is the Assessment Performed?
The final opinion is produced by integrating multiple sources of information. The polygraph examination is one component of a broader structured assessment. No single component determines the final opinion.
The assessment integrates:
Structured forensic interview
Systematic pre-examination interview to establish the scope and detail of the examined account
Statement analysis
Evaluation of the structure, consistency and content of the examined account
Memory evaluation
Consideration of trauma, time, reconstruction and the characteristics of the reported memory
Psychophysiological examination
Structured polygraph recording of cardiovascular, respiratory and electrodermal activity
Collateral case information
Relevant collateral material where available and appropriate
Recognised limitations
Explicit consideration of factors that may affect the reliability of the findings
Bayesian analysis
Structured evaluation of the strength of evidential support using Bayesian methods
Professional examiner judgement
The qualified practitioner's professional assessment, informed by all available information
No single component determines the final opinion. The assessment is a structured forensic opinion, not an automated statistical output.
How Statement Verification Testing Works
Statement Verification Testing (SVT) is a structured examination method in which the examinee prepares a detailed written account of the events to be assessed before the examination takes place.
Before the examination, the examiner reviews the written statement with the examinee. During this review:
- Ambiguous wording is clarified
- Opinions, assumptions and legal conclusions are removed where possible
- The statement is organised into clear factual events
- Examination questions are developed directly from the written statement
During the examination, physiological responses are recorded while the examinee answers questions relating to the specific events described in the written statement.
The purpose of SVT is to assess the credibility and internal consistency of the examined account rather than to prove that historical events occurred.
Preparing Your Statement
If you are asked to prepare a written statement for an SVT examination, your statement should:
- Describe observable events
- Use concrete behavioural descriptions
- Avoid speculation
- Avoid assumptions about another person’s thoughts or intentions
- Avoid legal conclusions
Instead of
“He sexually assaulted me.”
Prefer
“He removed my clothing without my consent.”
Instead of
“He imprisoned me.”
Prefer
“He blocked the doorway and prevented me from leaving.”
Factual descriptions generally allow more precise examination questions to be developed, which may improve the quality and defensibility of the examination.
Statement Verification Testing
Where this service is considered appropriate, The Centre for Forensic Neuroscience will generally use SVT rather than repeated direct questioning about the alleged traumatic event.
This means the examination is focused on whether the examinee maintains the credibility and accuracy of a specific written disclosure or account. This approach may reduce the need for repeated traumatic recall, while keeping the examination focused, structured and professionally defensible.
This does not mean that trauma-related responses can be eliminated. Trauma, distress, dissociation, anxiety or vulnerability may still affect suitability and interpretation. For that reason, every case is subject to screening, informed consent and safeguarding review before any examination is accepted.
Important Limitations
SVT evaluates physiological responses to questions derived from a written statement. It is important to understand the following limitations:
- SVT does not establish that historical events objectively occurred
- SVT does not replace police investigations
- SVT does not replace judicial fact-finding
- SVT findings should always be interpreted alongside all available information
Because SVT evaluates a broader narrative rather than a narrowly defined single issue, it may be less precise than a conventional specific-issue polygraph examination. This is an accepted methodological limitation of the approach.
SVT findings should be considered as one component of a broader assessment, not as a standalone determination.
Understanding Historical and Traumatic Memory
Historical abuse allegations involve memory for events that may have occurred years or decades ago. Memory science indicates that traumatic memory is often fragmented, that memory evolves and may be reconstructed over time, that confidence in a memory is not equivalent to its accuracy, and that inconsistencies in recall do not necessarily indicate deception.
The assessment considers these factors rather than assuming that perfect recall is expected. Physiological responses are interpreted with an understanding that trauma, emotional arousal and the passage of time may influence both the account and the examination process.
The assessment does not assume that inconsistency equates to deception, or that consistency equates to accuracy.
Suitability Screening
Every case is screened for psychological wellbeing, vulnerability, medical factors, trauma-related symptoms, dissociation and whether the examination is clinically and ethically appropriate.
Professional Support
The Centre for Forensic Neuroscience considers safeguarding status, legal or professional support, clarity of the referral question and any indication of coercion or pressure.
Declining Cases
Trauma-related symptoms may affect the suitability of the assessment and will be considered during screening. The Centre for Forensic Neuroscience may decline an assessment where welfare, safeguarding, trauma-related or professional concerns are identified.
Interpreting Findings
Any opinion is investigative rather than evidential. It is based on the structured integration of statement analysis, psychophysiological data, Bayesian analysis and professional judgement. Findings should be considered alongside other information, including witness evidence, documentary material, digital evidence, clinical information, safeguarding information, legal advice and other investigative material.
Examination findings should never be viewed in isolation.
Bayesian Credibility Assessment
Bayesian analysis is used to evaluate the strength of evidential support provided by the examination findings. It provides a structured method for assessing how strongly the available evidence supports one interpretation of the examined account compared with another.
Bayesian analysis does not calculate the probability that abuse occurred. The Bayesian analysis estimates the extent to which the observed examination findings provide greater evidential support for the proposition that the examined account is credible and internally consistent than for the competing proposition.
The result is expressed as a Bayes Factor—a measure of evidential support, not proof. A Bayes Factor of 10, for example, means that the examination findings are 10 times more likely to be observed if the examined account is credible and consistent than if it is not. This is a statement about the relative strength of evidential support, not about the probability of a past event.
Bayesian analysis increases confidence in the assessment by quantifying uncertainty, but it does not eliminate uncertainty.
Investigative Concern Bands
Evidential support framework
Where appropriate, findings are communicated using Investigative Concern Bands. These bands describe the degree of investigative concern arising from the examination findings. They relate only to the credibility and consistency of the examined account.
Very Low Investigative Concern
The examination findings provide strong support for the credibility and consistency of the examined account. No physiological indicators of concern were identified.
Low Investigative Concern
The examination findings are generally consistent with the examined account. No significant indicators of concern were identified in relation to the issues assessed.
Moderate Investigative Concern
Some indicators of concern were identified. While the findings do not support definitive conclusions, they suggest that aspects of the account may warrant further clarification, investigation or corroboration.
High Investigative Concern
Significant indicators of concern were identified in relation to the issues assessed. The findings suggest that substantial caution should be exercised and that further investigation or independent corroboration is appropriate.
Very High Investigative Concern
The examination findings raise serious concerns regarding the credibility and consistency of the examined account. The available evidence does not support the account as presented and further independent investigation is strongly indicated.
Investigative Concern Bands are not measures of guilt, innocence or factual truth. They should not be interpreted as probabilities that an allegation is true or false.
The absence of investigative concern does not establish that an alleged event occurred. The presence of investigative concern does not establish that an alleged event did not occur. Findings should always be considered alongside all available evidence.
Illustrative Forensic Example
The following is a hypothetical example illustrating how examination findings might be reported. It is provided for illustrative purposes only and does not represent any individual case.
Bayes Factor
9
Posterior Odds
9:1
Posterior Probability
0.86
95% Credible Interval
Above neutral prior
Posterior probabilities are calculated assuming the analytical model and the prior odds specified. This example assumes neutral prior odds (1:1), meaning no prior assumption is made about the credibility of the examined account before the examination findings are considered. Different prior odds would produce different posterior probabilities.
Investigative Concern Band
Low Investigative Concern
“The Bayesian analysis estimates that the observed examination findings provide substantially greater evidential support for the proposition that the examined account is credible and internally consistent than for the competing proposition. No significant physiological indicators of concern were identified. The analysis indicates that this conclusion remains robust when uncertainty is taken into account.”
This opinion does not establish that the alleged abuse occurred. Rather, it reflects the extent to which the examination findings support the credibility and consistency of the examined account within the defined scope of the assessment.
The Role of Professional Judgement
Bayesian analysis assists interpretation but does not replace professional judgement. The final opinion is a structured forensic opinion rather than an automated statistical output.
The final opinion reflects the integration of:
Statement analysis
Psychophysiological findings
Collateral information
Examination quality
Recognised limitations
Bayesian evidence
Professional forensic judgement
The overall opinion should be understood as a carefully considered professional assessment, not an automated output.
What This Assessment Cannot Determine
The assessment has clearly defined limitations. Findings should always be considered alongside all available evidence.
The assessment cannot prove that abuse occurred or establish the factual truth of any allegation.
The assessment cannot disprove an allegation or invalidate a disclosure.
The assessment cannot identify an offender or determine who committed an alleged act.
The assessment cannot determine criminal guilt or innocence, civil liability or evidential admissibility.
The assessment cannot replace police investigation or serve as a substitute for criminal proceedings.
The assessment cannot replace corroborating evidence or independent investigative material.
Findings cannot be interpreted in isolation from the wider evidential, safeguarding and investigative context.
The process should not be used coercively or under pressure. The Centre for Forensic Neuroscience will only consider an assessment where the proposed referral is voluntary, appropriately supported and professionally suitable.
Support and Safety
If you are experiencing domestic abuse, stalking, harassment, or feel at immediate risk, a forensic credibility assessment is not a substitute for safety planning, safeguarding support, police assistance, legal advice or clinical care.
If you require support, you may wish to contact:
- National Domestic Abuse Helpline: www.nationaldahelpline.org.uk
- National Stalking Helpline: www.suzylamplugh.org
You may also find support from the following organisations:
- Rape Crisis England & Wales: rapecrisis.org.uk
- SurvivorsUK: www.survivorsuk.org
- Victim Support: www.victimsupport.org.uk
If you or someone else is in immediate danger, call emergency services.
Discuss Suitability Before Arranging an Assessment
Every case is different. A confidential consultation is required before any examination is accepted.
Contact The Centre for Forensic Neuroscience