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Legal Mind Case and Commentary No 23: Reasoning and Logic in Psychological/Psychiatric Evidence [Koch HCH, Crowther-Green H and Nokling K, 2019]

18/10/19. This is the twenty-third in a series of Case reports and Commentaries from Prof Koch and colleagues.

Legal Mind Case and Commentary No. 23

Background: Yah v. Medway NHS Foundation Trust (2018) EWHC 2964 (QB)

I have summarised below several cases which were reviewed by Ward (1999) in his excellent article “Psychiatric evidence and judicial fact-finding” in the International Journal of Evidence and Proof (E and P, 3(3), 180-194).

We know that in many cases there is an interaction between concepts of Psychological Injuries, Evidential Reliability and Expert Witness behaviour and practice, case law analysis helps, in many cases, to clarify these issues (Koch, 2019 (a) and (b)).

These three concepts and their analysis offer a contemporary insight (Koch, 2019 (c)) into how personal injuries are considered and how judicial and expert opinion formation occurs, both in a positive and, at times, a negative manner (See Fig. 1 below).

Fig 1 Interaction between injuries, evidence and reliability


In his seminal article, Ward (1999) summarised a series of personal injury cases which illustrated the complexity of psychological injury and ‘nervous shock’ cases.

1. Vernon v. Bosley (1995): 68 days of evidence, 132 pages judgment and 3 Court of Appeal hearings.

2. Page v. Smith (1995): Reaching House of Lords on a point of Law and then a second Court Appeal Hearing.

3. Arrowsmith v. Beeston (1998): Insufficient time spent “to absorb very sophisticated psychiatric evidence”.

4. Abada v. Gray (1997): Court of Appeal informed that the Trial Judge must have based his decision on his “impression” of the expert witness, rather than evidence itself.

5. Pickford v. ICI (1998): Over-emphasis placed by trial judge on the expert’s demeanour.

Ward’s (1999) thesis was that most evidential conflicts between types of psychological evidence was relatively easy and rational but aided by an understanding and awareness of, amongst others, the following variables:

Narrative Coherence

Credibility and the claimant’s story

Analogical reasoning

Complexity and Uncertainty

I will take these, as Ward did, in turn with the aim of raising awareness of each variable which will be expanded in more detail and with more case analysis and reference in due course.

  1. Narrative Coherence

Narrative coherence is important in fact finding. The narrative shapes the assessment and prognosis. Increased coherence helps. Reduced coherence emphasises an unexplained story, with logical inconsistencies, in which a poorly constructed narrative contains ambiguous connections between events, and an increased, likelihood of a conclusion of ‘ mere coincidences’.

  1. Credibility and the claimant’s story

A significant and large percentage of medico-legal reporting rests on claimant’s self-report, hence the credibility of that claimant in how the information is presented is crucial. The judge’s assessment of unreliability, unconscious exaggeration or symptom distortion can provide a relatively simple explanation of claimant’s presentation and narrative (Koch, Mushati and Francis, 2019). In Pickford much of the disagreement, according to Ward, between the appellate judges centred on whether the trial judge’s assessment that the claimant was not consciously seeking to mislead the court could be reconciled with his finding that she had exaggerated her symptoms, and whether there was any plausible middle ground between conscious simulation and a genuine (psychological or) organic condition.

  1. Analogical reasoning

Ward (1999) stated that “Law, medicine and ‘common sense’ reasoning about causality” (and by implication diagnosis and prognosis) all involve classifying facts to determine whether they fall within the scope of rules or generalisation. Reasoning by analogy is important here. For example, in Page V. Smith, the issue was whether the minor car accident, suffered by Ms Page, fell within any category of known causes of chronic fatigue syndrome. Ralph Gibson LJ disagreed with Otto. J that the lack of comparable examples of this (observed or reported) is the expert’s clinical experience characterised the facts of a very low level of abstraction (I.e. logic).

In this and other cases (e.g. Gates V. McKenna (1998), the inability to point to specific precedents was a serious weakness.

Reference was made to the relevance of certain diagnostic criteria as in DSM 3 or 4 (American Psychiatric Association Certification) and what the legal position should be if DSM criteria were not overtly met. This is often a question for ‘the good sense of the judge “rather than strict adherence to DSM criteria.”

  1. Complexity and Uncertainty

Psychological/Psychiatric opinion can, at times, cause difficulties in understanding and agreement for two main reasons: volume of evidence, including inherent complexity, and/or ‘wood for the trees’ effects, and evidential uncertainty and a difficulty tolerating this.

Excessive attempts to connect ‘fragments of (a claimant’s) past by the claimant, exposed or judge, can result in an unreliable and “large number of mosaics” which result in unsafe and illogical causation assumptions.

In addition to arguing for the uniqueness of a claimant’s individual case and care, arguments can be forwarded to link an index event with clusters of symptoms or disorders which have insufficient clinical backing in this particular personal injury context.

A reliable and concise narrative needs to be compared with the body of medical knowledge available. The three cases of Page V. Smith, Abada v. Gray and Pichford v. ICI involved disputes about general medical questions such as the nature and causes of CFS Chronic Fatigue Syndrome, Schizophrenia and Repetitive Strain Injury (RSI). These were recommended by the judge as ‘scientific questions of great difficulty and of strong uncertainty’.

All parties, especially Judges and Experts develop a tolerance for the uncertainty and at times, unreliability of evidence and information placed before them.


A review of cases where psychological/psychiatric evidence has been disputed illustrates that personal injury cases frequently involve complex issues of causation, diagnosis and prognosis. The concepts and methods of reasoning in psychology and psychiatry are relevant close to those of everyday judicial reasoning (Ward, 1999) and hence disputes which arise are easier to resolve than many others in Tort law. Coherent reasoned opinions and its evaluation should typically rank above the assessment of demeanour or whether to trust an expert or not.

List of cases

(1995) 28 BMLR 1 Vernon V Bosley

(1995) 2 A11 ER 736. Page V Smith

Lawtel 18 June 1998 (CA.) Arrowsmith v. Beeston

(1997) 40 BMLR 116. Abada v. Gray

(1998) 1WLR 1189 Pichford v. IC

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