Brown v Morgan Sindall Construction and Infrastructure Ltd [2025] EWHC 2204 (KB):

Clarifying the role of validity testing in expert evidence

 

Following last month’s case update by Professor Keith Rix of Brown v Morgan Sindall, several experts have offered further reflections on the use of validity testing in medico-legal assessment. Commentaries from Professor Michael Kopelman (neuropsychiatry), Dr Karen Addy (neuropsychology), Mr Daniel Friedland (neuropsychology) and Dr Kathryn Newns (clinical psychology) were published in the MAEP Expert Witness Healthcare Matters newsletter, coordinated by Professor Rix.

This follow-up brings together the key points emerging across disciplines. It also clarifies several areas regarding the early learning points given in the September case update. The discussion below refines those conclusions and reflects current multidisciplinary consensus.

Professor Rix's September case update is republished below. 

Context of the case

The claim concerned an orthopaedic injury with subsequent PTSD symptoms. There was no claimed neurological injury. Validity testing therefore arose in a mental health rather than neuropsychological context.

The judgment highlighted challenges when experts rely on psychometric data that cannot be fully scrutinised in court. It also raised questions about qualification, transparency and the limits of expertise.

Clarifying key issues

• Different forms of validity testing: Performance Validity Tests (PVTs) evaluate the credibility of test performance within neuropsychological assessments. Symptom Validity Tests (SVTs) evaluate the credibility of reported symptoms and can be appropriate in broader mental health contexts. The two are not interchangeable.

• Appropriate training and use: Psychiatrists, clinical psychologists and neuropsychologists may use psychometric measures only within their scope of training, licensure and competence. Administering SVTs or PVTs requires a working knowledge of their purpose, limitations, normative data and interpretive frameworks. Using measures without that foundation risks error and misinterpretation.

• Disclosure and transparency: While item-level test materials should not be released due to licensing restrictions, experts can and should name the tests used, describe their purpose, report scores and cut-offs, and explain their interpretive relevance. From the judgment, it remains unclear whether this occurred in Brown v Morgan Sindall.

• Integration with clinical evidence: Validity testing results must be interpreted alongside clinical history, observed behaviour, and collateral data. They are one component of a holistic assessment, not a stand-alone determination.

• Malingering and expert limits: Experts may describe inconsistent or exaggerated responding, but ultimate judgments of intent or dishonesty rest with the Court.

Updated learning points

1. Clarify purpose: Distinguish between PVTs, SVTs and other psychometric measures; they have distinct roles.

2. Stay within competence: Use only those tests for which you have appropriate training, supervision and access rights.

3. Be transparent: It is highly likely to be appropriate to name the tests administered and report scores but never release protected materials.

4. Integrate evidence: Interpret validity findings within the broader clinical and contextual picture.

5. Respect judicial boundaries: Report on effort, consistency and credibility—but leave determinations of malingering to the Court.

This cross-disciplinary exchange has helped refine understanding of how validity testing should (and should not) be used in expert evidence. It underscores the importance of professional training, test security, and clear communication with the Court.

Readers seeking a fuller overview of the discussion may refer to the September 2025 Bulletin for the case summary and to the October issue of MAEP Expert Witness Matters for the extended commentaries.

 

 

Brown v Morgan Sindall Construction and Infrastructure Ltd [2025] EWHC 2204 (KB): Reliance on performance validity tests administered by psychiatrists (First published by EWI on 9 September 2025)

Professor Keith Rix

 

Commentary

This is a very important judgment for psychiatrists and psychologists who employ validity testing when assessing litigants. There were two experts, both psychiatrists. One employed validity tests. The other did not and she professed no experience of their use. The psychiatrist who employed them was a registered user of the tests for the administration of which he had been trained and had paid for a licence.

Reliance on the results of validity testing was called into question for a number of reasons:

• There were contextual limitations specifically regarding psychological and physical health variability, the potential for bias, a possible overemphasis of malingering detection and a potential lack of holistic assessment.

• The defendant sought to advance expert evidence as that of a neuropsychologist, which the defendant’s expert was not.

• The use of so many tests within a medico legal context, particularly when administered by a defendant psychiatric expert may have led to a lack of holistic assessment.

• The claimant’s performance could have been impacted by his dyslexia.

• The validity testing results was evidence that was not admissible as expert evidence.

• If it was admissible, permission to adduce this particular form of expert evidence, given that qualification as a psychiatrist does not automatically provide the expertise necessary to administer the tests, should not have been granted.

• If it was admissible, it was unfair and should be treated with caution or disregarded.

• There had been unjustified and inappropriate non disclosure of the tests and answers given.

• This evidence did not, because the expert was neither a psychologist or neuropsychologist, have the ability to explain fairly the range of opinion on the subject of validity testing in compliance with CPR 35 PD (6): where there is a range of opinion on the matters dealt with in the report –(a) summarise the range of opinions.

• Not putting the tests into the public domain impacts upon the evidential and probative value of the outcome of the tests within an adversarial court setting.

• The claimant's legal representatives had been limited to the extent to which they had been able to probe, question or challenge that opinion evidence, again, because they had been denied sight of, or an understanding of, the underlying material upon which it was based.

• An expert's report must give details of any literature or other material which has been relied on in making the report which can be considered to include the questions and answers that Claimant gave.

• In the absence of an application for permission to rely upon this type of expert evidence, there was a risk of disadvantage to the other party, particularly when that was combined with the limited disclosure of the tests and responses given by the Claimant.

• There was, at least, a real possibility that there were different views as to consensus as to the reliability of validity testing in the UK, albeit that it is more widely used in North America.

Psychologists have more experience of administering validity tests and a further commentary on this case is being sought from an experienced psychology expert. Advice for psychologists is to be found in Guidance on the assessment of performance validity in neuropsychological assessments (https://cms.bps.org.uk/sites/default/files/2022-07/Guidance%20on%20the%20assessment%20of%20performance%20validity%20in%20Neuropsychology%20assessments.pdf )

In the meantime, psychiatrists who intend to use validity testing are advised to inform their instructing solicitors in order that they can consider advising the adverse party and / or the court. This will provide the opportunity for the court to consider whether such evidence is admissible and, if it is, ensure that the adverse party, if it wishes to do so, can instruct a neuropsychologist or suitably qualified psychiatrist.      

Learning point

• When assessing a subject, have regard to and be prepared to explain the possible effects of the subject feeling rushed, feeling the assessment oppressive, or considering questions inappropriate or intrusive.

Case

The Claimant was cycling home from work. He travelled along a cycle lane on Pitfield Street, London located next to a construction site. As part of the construction work, the relevant part of Pitfield Street had been closed to motorised vehicles and a different layout of the cycle route established: a two-way cycle lane within one carriageway of the road. The Claimant fell from his bicycle. It was immediately apparent that he had sustained an injury to his elbow. Emergency services were called, and he was taken to hospital. He lost a significant amount of blood and required a blood transfusion. He underwent surgery, and was able to leave hospital and return home some 4 days later.

The Claimant sought compensation from the Defendant in respect of the injury and losses. There was no dispute that after the accident the Claimant suffered from depression and PTSD, although there was a dispute as to the extent of and degree of those symptoms. Significantly, the Defendant alleged that the Claimant was malingering and had exaggerated his symptoms

Expert psychiatric evidence

The Claimant relied upon the expert evidence of Dr Gibbons, Consultant Psychiatrist. Dr Gibbons produced three expert reports dated August 2022, July 2023 and 13 March 2025. The Defendant relied upon the evidence of Dr Wise, Consultant Psychiatrist. Dr Wise produced two reports dated 30 May 2023 and 25 March 2025.

There was a degree of agreement between the experts. In the joint report Dr Wise and Dr Gibbons agreed

(i) That from C's description of events and his symptoms he meets the diagnostic criteria for PTSD.

(ii) After treatment for PTSD there is a good prognosis expected, albeit the experts had different opinions as to the number of treatment sessions required (Dr Wise, up to 12 sessions and Dr Gibbons up to 26).

In Dr Wise's opinion, the Claimant met a number of criteria for malingering. He opined that if that evidence was accepted, it was difficult to know how impaired the Claimant actually had been or was. Dr Wise also considered that the Claimant met the criteria for an alcohol misuse problem.

Dr Gibbons expressed reservations about the tests carried out by Dr Wise in order to reach his opinion that the Claimant met relevant criteria for malingering. These tests were, broadly, referred to as 'validity' testing/ 'symptoms validity testing' or 'performance validity tests'. Dr Gibbons expressed concern regarding the contextual limitations of the evidence advanced by the Defendant (through the opinion evidence of Dr Wise), specifically regarding psychological and physical health variability, the potential for bias, a possible overemphasis of malingering detection and a potential lack of holistic assessment.

In an opening document prepared by the Claimant, it was submitted that the Court must have regard to the domain within which Dr Wise and Dr Gibbons gave their expert opinion: Dr Gibbons is a psychiatrist, not a neuropsychologist and, it was submitted, her expert evidence, properly so called, was limited to her area of expertise. It was submitted that to the extent that Dr Wise sought to advance expert evidence as a neuropsychologist, or to the extent that he had formed his expert opinion on the basis of that area of expertise, that evidence was not properly admissible.

As set out above, Dr Wise prepared two reports. After the assessment which led to the first report, the Claimant prepared a witness statement. The evidence was that was prepared before disclosure of Dr Wise's report to the Claimant. The Claimant set out his subjective experience of the appointment. He found the appointment difficult, at times oppressive. He was concerned about the appointment and its consequences.

The two psychiatric experts had different opinions and based those opinions on different assessments. Dr Gibbons performed what might be described as a traditional, holistic assessment. Inevitably this required her, to some significant extent, to base her opinion on self report. Her assessment was holistic, and her opinion one she reached against a background of extensive experience in psychiatry. She perceived the Claimant to have cooperated in the assessment and to have been genuine and open.

Dr Wise relied significantly upon the results of validity testing carried out during his assessment.

Dr. Gibbons questioned the use of so many tests within a medico legal context, particularly when administered by a defendant psychiatric expert. She considered that there was a risk that their use may have led to a lack of holistic assessment.

Dr Wise considered that the Claimant performed particularly badly within the tests he performed and, further, that that poor performance could not be adequately explained by the Claimant not trying during the assessment. This was because he stated that the Claimant had, in response to a question, stated that he had tried his best during the tests. He did not consider that the performance could have been impacted by the Claimant's dyslexia, nor by any other factors.

On balance, the judge preferred the evidence of Dr. Gibbons. She said that she gave her evidence in a straightforward and measured way. She was impressive. She conceded the limitations of her assessments and did not profess expertise in areas where she had none. Her report might be described as 'brief', but it was clear, readily understandable and, in my judgment reflected that which she described she had undertaken, a thorough and holistic assessment of the Claimant taking into account relevant evidence.

Her assessment of the Claimant as being genuine in that which he said, but at pains to persuade others of the impact the accident had upon him and different aspects of his life, resonated with that which the judge heard and saw in evidence. She also considered that her evidence that his account was impacted by the depression he had lived with was very likely to be accurate.

Dr Wise gave clear evidence and sought to assist the Court within his area of expertise. He did, in my judgment, rely heavily upon the validity testing he performed. As set out below, I consider that there are real limitations with the evidential value of those tests without the Court and parties' ability to understand and scrutinise the tests and responses.

The Claimant made a number of submissions regarding Dr Wise's evidence to the extent that it relied upon the validity tests administered. These included that the evidence was not admissible as expert evidence, that if it was, permission to adduce this particular form of expert evidence (given that qualification as a psychiatrist does not automatically provide the expertise necessary to administer the tests) should not have been granted; that there had been unjustified and inappropriate non disclosure of the tests and answers given; that the test results were not admissible, alternatively, unfair and should be treated with caution or disregarded; that Dr Wise's evidence did not (because he is neither a psychologist or neuropsychologist) have the ability to explain fairly the range of opinion on the subject of validity testing in compliance with CPR 35 PD (6) where there is a range of opinion on the matters dealt with in the report –(a) summarise the range of opinions.

Having set out above, the judge’s primary conclusion in respect of this aspect of the case rested upon her assessment of the witness evidence which she heard and saw. Her initial impression of the Claimant's evidence was supported and corroborated by the evidence of his wife and a work colleague, both of whom the judge considered to be impressive witnesses.

In respect of the validity testing, she made the following points:

a. The tests administered and the responses given by the Claimant were not in evidence before the Court. This was because, as Dr Wise explained, in order to be able to administer those tests he was required to be trained to a suitable level and then had to purchase a license to use the tests. A condition of him being granted that license was that he could not disclose the detail of the tests, nor the questions administered. This was because, if those tests enter the public domain, there is a risk or likelihood that people who would be subject to the tests would begin to be able to access information which would enable them to give responses more likely to generate a particular outcome to them. That would mean, that the tests would be less valid because, over time, their results would become 'skewed' by the knowledge base developed about responses which would elicit a particular result.

b. There may be good commercial and other reasons for not putting the tests into the public domain. However, that impacts upon the evidential and probative value of the outcome of the tests within an adversarial court setting. It is ultimately for the Court to assess the credibility of witnesses and to determine whether they are or have been honest or dishonest. In reaching that conclusion a Court must consider all available evidence. That includes, significantly, expert evidence where appropriate. Dr Wise was precise in his evidence. His expert opinion was not that there was a 99% chance that the Claimant was malingering. Rather, his opinion was that the policy document of the AACN (the American Academy of Clinical Neuropsychology) has stated that failures on three relevant validity tests rates the probability of malingering to be over 99%. Dr Wise' opinion, based on this information and the test outcomes from the Claimant's assessment was that the matrix of evidence indicated exaggeration or feigning that that things were not as described. However, the Court was limited in its ability to evaluate the strength of that opinion without sight of, or an understanding of, the underlying material upon which it was based.

c. In addition, the claimant's legal representatives had been limited to the extent to which they had been able to probe, question or challenge that opinion evidence, again, because they had been denied sight of, or an understanding of, the underlying material upon which it was based. The importance of being able to undertake that analysis can be seen from the fact that, during evidence, scrutiny of the AUDIT test scores which were before the Court revealed that a simple error had occurred in the adding up of those scores. That was only identified in cross examination, and after the material had been seen by the Claimant and his representatives.

d. Finally,

i. The Claimant, in submissions, appropriately drew the court’s attention to CPR PD 3.2 (2) which provides that an expert's report must give details of any literature or other material which has been relied on in making the report. The Claimant submitted that this must include the questions and answers that Claimant gave. For the reasons set out above, the judge considered that there was merit in this submission.

ii. She agreed with the submission made that the need for permission to be granted for expert evidence is an important procedural step in litigation which can prevent ambush and imbalance of arms. Dr Gibbons could provide limited assistance to the Court regarding the tests. She does not use these types of tests, nor have qualification to rely upon them. The evidence of Dr Wise was that specific training was required to administer the tests. There was, in her judgment, strength in the submission made that, in the absence of an application for permission to rely upon this type of expert evidence, there was a risk of disadvantage to the other party, particularly when that was combined with the limited disclosure of the tests and responses given by the Claimant.

e. From the evidence before the Court it appeared that there was, at least, a real possibility that there were different views as to consensus as to the reliability of validity testing in the UK, albeit that they are more widely used in North America. It appeared that this a developing field with potential complexity, for example, about the impact of conditions such as depression on scores.

Further, the judge considered that there were a number of factors which were likely to have impacted upon the results all of the assessment undertaken by Dr. Wise. First, the Claimant had not appreciated how long the appointment would take. That was his error and his mistake for which there was no justification. He accepted that. Nonetheless, the judge accepted his evidence that he had made that mistake. He attended in his lunch hour believing that the assessment would be significantly shorter than it was. During it, he felt under pressure, both the pressure of time and, the pressure of the situation: being assessed by the Defendant psychiatrist in respect of his injury. He perceived the assessment to be intrusive and overly extensive. For example, he could not understand why he was being asked questions about his childhood or any adverse childhood experiences. That added to his sense of agitation and unease.

The Claimant is dyslexic. He had not informed Dr. Wise of that in advance, or during the assessment. He found the forms difficult to complete. The judge believed his evidence about that and also that of his wife, that form filling was something that she undertook, not the Claimant because he found it difficult. Finally, the judge considered it likely that, as these different factors came into play, the deteriorating relationship and rapport between Dr Wise and the Claimant was not conducive to a successful assessment, by which she meant an assessment which achieved the most accurate outcome. She believed the Claimant's oral evidence that he simply wanted to get out of the meeting and rushed. Consequently, she considered it likely that his response to the question "have you tried your best?" was inaccurate and positively misleading.

The fact that the appointment was difficult was supported by the statement prepared by the claimant in advance of receipt of Dr Wise's report in which he set out his concerns about the appointment. The timing of that statement, evidentially, supported the fact that the Claimant felt that the appointment was a difficult one and had not gone well. It might be less likely to suggest that the Claimant faked concern about the appointment because the issues he raised were raised before he knew about the outcome of the tests, particularly the validity tasks.