KA-2024-BHM-000008 - [2025] EWHC 2093 (KB)

Grounds relating to the cyclospora issue

It is submitted on behalf of the Appellant that the judge erred in the following respects:

Ground 1. He misunderstood the evidence about testing for cyclospora oocytes and proceeded on the basis that the tests were binary, so that either the regional laboratory’s test result was wrong or the national reference laboratory’s test result was wrong. In fact, the evidence showed that there will be a “false negative” result in some 34% of cases. This means that the negative test for cyclospora in the national reference laboratory’s test did not undermine or discredit the positive result in the regional laboratory’s test;

Ground 2. The judge failed to appreciate that all of the expert witnesses agreed in their evidence that the single positive result in the regional laboratory test was enough to make it “probable” that the Appellant had been infected by cyclospora. In particular, the judge misunderstood or mis-recalled the evidence of the microbiology expert called by the Respondent, Dr Gant. He had agreed to a proposition put to him in cross-examination that it was probable that the Appellant had been infected by cyclospora. Properly understood, Dr Gant had not resiled from this in re-examination. Rather, he had said that “in all the circumstances”, it was likely that the Appellant had not been infected by cyclospora. The “circumstances” included the proposition that the Appellant had started to feel ill before she travelled to Mexico, which proposition was rejected on the facts by the judge;

Grounds 3 and 4. Moreover, the judge did not appreciate that a single positive result is enough to mean that the presence of the cyclospora pathogen was “probable”. The purpose of second test was to turn the result from “probable” to “certain. Therefore, the positive result in the regional test was sufficient proof, for the purposes of the civil standard of proof, that the Appellant had been poisoned by the cyclospora pathogen. The negative result in the national reference laboratory test does not detract from this. The judge did not give adequate, if any, weight to the numerous scientific papers which supported the Appellant’s case in this regard;

Grounds 5 and 6(a) to (e). The judge did not give adequate reasons for rejecting the evidence in support of the contention that the scientific evidence proved on a balance of probabilities that the Appellant had ingested cyclospora.

In his oral submissions, Mr Pennock emphasised the following points in relation to the cyclospora issue:

The judge did not address or deal with the potential explanations for the different laboratory results, such as that cyclospora oocytes are very low shedding (i.e. they may be found in very small numbers in stool samples) and so there might have been one or a few oocytes in the slide from the stool sample that was used by the regional laboratory and no oocytes at all in the slide that was used by the national reference laboratory. Also, there was evidence that the different laboratories used different techniques;

Mr Pennock submitted that the answers given by Dr Gant at the end of his cross-examination and during re-examination “destroyed” the defence case. Mr Pennock submitted that the answer in re-examination that is relied upon by the Respondent, to the effect that “in this specific case”, Dr Gant did not think that the laboratory reports were good evidence of cyclospora, is invalidated, because what Dr Gant was thinking about, in his reference to the specific case, was his mistaken belief that there was evidence that the Appellant was ill before she went to Mexico. The judge failed to consider or to deal with whether the finding that the Appellant fell ill whilst in Mexico undermined Dr Gant’s evidence on the cyclospora issue.

The judge was plainly in error when he said that the regional laboratory was Dr Threfall’s laboratory.

Mr Pennock said that Dr Gant’s view that the national reference laboratory was more expert and experienced than the regional laboratory was an unsubstantiated assertion, for which there was no evidence.