Once there was credible evidence that he may have been suffering from CI then it was for the prosecution to disprove it.
This is I think the crux of the matter for many of us experienced pilots. I wasn't at the trial, I haven't seen nor have I read the evidence transcripts. But, I have difficulty reconciling that credible evidence, as reported from the court, with personal experience. It is those personal experiences that the jurors did not posses. Perhaps that is both a strength and weakness of trial by jury and adversarial trials.