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Legal Mind Case and Commentary No 29: Risks of Unbalanced and Misleading Expert Evidence - Koch HCH, Medley A and Pelser C, May 2020

This is the twenty-ninth in a series of Case reports and Commentaries from Professor Koch and colleagues.

Case: Watts v. Sec. of State for Health [2016] EWHC 2835 (QB)

Background: A case involving a serious birth injury raised issues of parental evidence reliability, consistency and accuracy. In addition, the quality of medical evidence was questioned.

This was a claim for damages for personal injury sustained by the claimant at birth on 6/9/1993 in Stoke Mandeville Hospital. The injury was a right brachial plexus injury (‘Erbs Palsy’), which left the claimant with permanent weakness and restrictive movement in the right upper limb.

This was acknowledged by the Court as a serious and distressing injury. The parents’ sincerity and honesty was not doubted. However, the accuracy of their recall was questioned. A draft letter written by the mother was altered and the central part of the case (the Erbs Palsy injury) was only briefly referred to. In the parents’ account, there was inconsistency in the chronology of events.

This resulted in the Court concluding that the parents’ evidence needed to be treated with caution and its reliability assessed ‘in the context of the evidence as a whole’.

The second issue was the matter of the expert witness medical evidence. Criticism levied at the claimant expert was as follows: -

1. Lack of experience in specific injury

2. Limited reference to relevant academic data

3. Lack of balanced opinion

4. Evasive on questioning

5. Several unjustified criticisms in report

6. Several unjustified criticisms and unexplained attempts to change her opinion in favour of the claimant at trial

7. Insufficient understanding of relevant anatomy and management of shoulder injuries

Overall, the basic duty of this expert witness to maintain objectivity and independence was questioned.

The claim was dismissed.

Commentary: As Simpson-Scott (2020) correctly noted, the adverse effect of the passage of time on evidential quality is a persistent problem in clinical negligence cases, in particular with Birth Injury cases. We also know that memory encoding and consolidation are disrupted after trauma and can result in fragmented recall of traumatic events. He referred to another case, Sanderson v. Guy’s and Thomas’ NHS Foundation Trust [2020] EWHC 20 (QB), finding the following factors to be relevant:

1. The quality of the available documentary evidence

2. The reduced quality of the witness’ recollection of events given the passage of time

3. The consequential ability of the experts to collate incomplete or unreliable evidence into a persuasive and robust opinion

The witness evidence needs to be consistent with the contemporaneous documents available especially in cases where a long period of time has elapsed.

Expert evidence forms a central plank in most C.N. cases. Accordingly, the more consistent the factual evidence is, the more persuasive the expert’s opinion is likely to be. Irrespective of the reliability and consistency of data, information and evidence available to the expert, the expert must practice objectivity, balance and independence when arriving at his/her opinion. Cognitive diversity (more than one point of view, often conflicting) has to be managed skilfully by the expert.

In the difficult circumstance in which the expert is minded to modify, alter or change his/her opinion a little or a lot, then clear and cogent explanation and rationalisation must be given to ensure robust logical appraisal of evidence has taken place.



Prof. Hugh Koch, Dr Andrew Medley and Dr Cara Pelser.

Professor Koch is visiting professor in Law and Psychology at Birmingham City University (

Dr Andrew Medley and Dr Cara Pelser are both Clinical Psychologists with Hugh Koch Associates.


Koch, HCH. (2016) Legal Mind: Contemporary Issues in Psychological Injury and Law. Expert Witness Publications.


Koch, HCH. (2018). From Therapist’s Chair to Courtroom: Understanding Tort Law Psychology. Expert Witness Publications. Manchester.

Koch, HCH. (2019). Legal Mind Case and Commentary: Publication Directory 2019. Expert Witness Publications. Manchester.

Simpson-Scott G (2020) Time Challenge. PI Focus March 6-9.

Previous commentaries have covered:

Koch, HCH, Davies M and Laraway A (2020) Legal Mind Case & Commentary No.28: Experts’ Joint Statements: Key Medico-Legal Issues. April. March 2020.

Koch HCH, Jansen F, Crowther-Green H & Francis A, March (2020) Legal Mind Case & Commentary No.27: PTSD in Road Traffic Accident: A review of key medico-legal issues. PIBULJ. March 2020.

Koch HCH, Milner P and McFadyen K (2020) Legal Mind Case & Commentary No.26: Psychological harm following sexual abuse. Procedural aspects of psychological assessment. PIBULJ. February 2020.

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