This blog has previously considered the issue of witness evidence. For example, on 8 August 2018 I looked at their credibility and probative value. In October 2019 the Court of Appeal, in Kogan v Martin & Ors  EWCA Civ 1645, had reason to revisit certain jurisprudence concerning the assessment of witness evidence, and the trial judge’s treatment of the same.
The facts of the case are not relevant for the purposes of this article. More relevantly Lord Justice Floyd delivered the judgment of the court and stressed two important factors:
(1) Witness recollection has to be assessed in its proper context:
88. We think that there is real substance in this ground of appeal. We start by recalling that the judge read Leggatt J’s statements in Gestmin v Credit Suisse and Blue v Ashley as an “admonition” against placing any reliance at all on the recollections of witnesses. We consider that to have been a serious error in the present case for a number of reasons. First, as has very recently been noted by HHJ Gore QC in CBX v North West Anglia NHS Trust  7 WLUK 57, Gestmin is not to be taken as laying down any general principle for the assessment of evidence. It is one of a line of distinguished judicial observations that emphasise the fallibility of human memory and the need to assess witness evidence in its proper place alongside contemporaneous documentary evidence and evidence upon which undoubted or probable reliance can be placed. Earlier statements of this kind are discussed by Lord Bingham in his well-known essay The Judge as Juror: The Judicial Determination of Factual Issues (from The Business of Judging, Oxford 2000). But a proper awareness of the fallibility of memory does not relieve judges of the task of making findings of fact based upon all of the evidence. Heuristics or mental short cuts are no substitute for this essential judicial function. In particular, where a party’s sworn evidence is disbelieved, the court must say why that is; it cannot simply ignore the evidence.
(b) The nature of transactions will dictate the importance, likelihood or anticipation of documentary corroboration:
89. Secondly, the judge in the present case did not remark that the observations in Gestmin were expressly addressed to commercial cases. For a paradigm example of such a case, in which a careful examination of the abundant documentation ought to have been at the heart of an inquiry into commercial fraud, see Simetra Global Assets Ltd & Anor v Ikon Finance Ltd & Ors  EWCA Civ 1413 and the apposite remarks of Males LJ at paras. 48-49. Here, by contrast, the two parties were private individuals living together for much of the relevant time. That fact made it inherently improbable that details of all their interactions over the creation of the screenplay would be fully recorded in documents. Ms Kogan’s case was that they were bouncing ideas off each other at speed, whereas Mr Martin regarded their interactions as his use of Ms Kogan as a sounding board. Which of these was, objectively, a correct description of their interaction was not likely to be resolved by documents alone, but was a fundamental issue which required to be resolved.
HHJ Pearce referred to the cases above in his judgment of 8 January 2020 in Donovan & Anor v Grainmarket Asset Management Ltd  EWHC 17 (Comm) and said:
“164. Each of the parties in this case attacks the evidence adduced by the opposing side on the grounds that the other’s witnesses, especially the leading players, are unreliable if not downright dishonest.
165. In considering the oral evidence in this case, including the significance and extent of any dishonesty and any attacks on the reliability of witnesses, I bear in mind the comments of Leggatt J (as he then was) in Gestmin v Credit Suisse  EWHC 3560 at paragraphs 16 to 20 cited by him and expanded upon in paragraphs 66 to 70 of his judgment in Blue v Ashley  EWHC 1928: “The best approach for a judge to adopt in the trial of a commercial case is to place little if any reliance on witnesses’ recollections of what was said in meetings and conversations, and to base factual findings on inferences drawn from the documentary evidence and known or probable facts.”
166. This valuable expression of the need to be cautious about accepting witness evidence does not of course entirely discharge the judge from the duty of making an assessment of witnesses and their evidence (see HHJ Gore QC in CBX v North West Anglia NHS Trust  WLUK 57, cited with approval in Kogan v Martin  EWCA Civ 1645). Even in a commercial case with the parties taking firmly entrenched positions, it is necessary to look with some care at the evidence of the main actors where that might provide valuable context and explanation.
167. It is a striking feature of this case, that in period when the business relationship between Mr Donovan and Mr Crader was breaking down in , they nevertheless remained on polite terms within emails and indeed seemed to show sympathy for the position of the other even if they did not accept it. That goodwill was also apparent during the witnesses’ oral evidence though it is singularly absent from their written statements. This might suggest that this court should not be too quick to find that the evidence of the witnesses has been adversely affected by the typical bad feeling that permeates commercial litigation. However, both sides made telling points about the reliability of the others’ witnesses that I bear in mind.”