The case of Curran v Collins  EWCA Civ 404 is a useful reminder to practitioners that a very high burden is placed on appellants seeking to challenge a decision on the issue of witness credibility. As Lady Justice Arden said in the judgment (para. 30) "...any appellant who challenges the judge's finding on credibility has a particularly difficult task."
The facts of the case were that the claimant, Ms Curran, was claiming a share in various properties owned by the defendant, Mr Collins. The claimant was unsuccessful at trial and part of her appeal rested on the findings made by the trial judge in relation to witness credibility.
There were two relevant witnesses:
Ms Curran: who the trial judge found gave evidence in a "completely open and frank way". The judge was perfectly satisfied that the evidence given was what Ms Curran "honestly and passionately believed to be the truth" (Judgment, para. 55). However, even evidence honestly given can be unreliable, according to the trial judge, and this can be for one of two reasons. Firstly, it can be because of the way the witness feels about the facts, as expressed in their evidence. Secondly, it can be because of their tendency to express themselves without precision. It was lack of precision in Ms Curran's evidence which led to the trial judge's finding that her testimony was not reliable. As opposing Counsel argued, "[s]he had strong emotions causing her to be overemphatic." The finding of lack of precision was based on Ms Curran stating under cross examination that she had "done all the paperwork" in relation to the business in dispute. This was not demonstrated to be true – she had in fact only done part of it. This lack of precision affected her credibility.
Mr Collins: who the trial judge found to be intelligent and capable of being very calculating, and whose evidence the trial judge approached with "extreme caution" because of lack of consistency. Nonetheless the trial judge preferred his account of events to that of Ms Curran. (Judgment, para. 71).
The Court of Appeal considered how an appellate court should approach issues of witness credibility. Arden LJ (paras. 29-33):
As I held in Langsam v Beachcroft LLP  EWCA Civ 1230:
It is well established that, where a finding turns on the judge's assessment of the credibility of a witness, an appellate court will take into account that the judge had the advantage of seeing the witnesses give their oral evidence, which is not available to the appellate court. It is, therefore, rare for an appellate court to overturn a judge's finding as to a person's credibility. Likewise, where any finding involves an evaluation of facts, an appellate court must take into account that the judge has reached a multi-factorial judgment, which takes into account his assessment of many factors. The correctness of the evaluation is not undermined, for instance, by challenging the weight the judge has given to elements in the evaluation unless it is shown that the judge was clearly wrong and reached a conclusion which on the evidence he was not entitled to reach. In other cases, where the finding turns on matters on which the appellate court is in the same position as the judge, the appellate court must in general make up its own mind as to the correctness of the judge's finding (see Datec Electronic Holdings v United Parcels Service  UKHL 23,  4 All ER 765,  1 WLR 1325 at 46 per Lord Mance).
Thus any appellant who challenges the judge's finding on credibility has a particularly difficult task. In this case, the appellant seeks to overcome the difficulty by asserting that the judge's finding was unsubstantiated or inconsistent or inadequately reasoned.
In my judgment, the judge was entitled to find that the appellant gave an inaccurate statement when she said that she did the paperwork for the Airedales. Her answer completely omitted the accounts that had to be kept. I prefer Mr McCue's interpretation of the transcript. Ms Crowther did not pursue any suggestion that the judge had improperly intervened in the cross-examination of Ms Curran.
The judge's finding on Mr Collins' credibility envisaged that she should have to exercise caution when considering his evidence. That meant that she would on some matters accept and some reject it. That does not amount to inconsistency. There is no suggestion that her acceptance or rejection of his evidence was against the weight of the evidence so that it was not open to her. The judge was not for this reason wrong to accept Mr Collins' evidence at times in her judgment.
I would therefore reject this ground of appeal."
The court's conclusion that Ms Curran "convinced herself" that she was telling the truth seemingly rests on this one example of imprecision – a cautionary tale for witnesses as they prepare to give evidence. On one hand witnesses need to be firm and stick to their guns when they give evidence but they must not stray into being overemphatic and making broad assertions / generalisations which do not stand up to scrutiny.