As someone who watched the defence’s comprehensive demolition of the prosecution case in the Old Bailey trial, and also someone who heard evidence from several prosecution witnesses that seemed to support the defence case, I would like to agree with everything Legalapproach says at post #505 above.
On the question of the existence or otherwise of CI in an aviation context, this is my understanding, which I hope might be helpful. I should stress that I am no expert on the subject.
Cognitive Impairment (CI)
CI is a not a medical condition - it is a symptom of one or more medical conditions.
Most, if not all, professional pilots are aware of CI, since it is the main symptom of altitude hypoxia, even if they have not heard the term.
Other causes of CI include alcohol (which some professional pilots are aware of!), and Transient Ischemic Attack (TIA) (more medical).
At the trial, cerebral hypoxia leading to CI was covered. Cerebral hypoxia again requires an underlying cause.
Whilst CI is not, or was not, a widely familiar term, I am aware of it's being quoted in MoD records around 2003.
The Service Inquiry into the death in 2011 of Flt Lt Jon Egging, Red 4, describes CI. It points out that it can occur in the recovery phase from G-LOC, and quotes examples.
A-LOC can involve, or lead to CI, although the Old Bailey trial highlighted differing opinions and research findings on the exact definition of A-LOC in ‘G impairment’.
As I understood the trial defence, AH’s pattern of mistakes and errors bore the characteristics of CI. The defence did not identify a specific cause of that CI; that would be for accident investigators to consider. The defence did raise the possibility that it could have been G-induced.
Hope that helps
airsound