Letby's barrister had the opportunity to seek permission to inform the jury of the investigations into Hindmarsh but didn't. Presumably he didn't think it would impact on the jury's view of Hindmarsh's evidence (which seems incredible, but there must be a reason for that decision). Or perhaps he thought it unlikely the order would be granted, in which case it suggests the investigation into Hindmarsh was so unrelated to his work for the prosecution that the judge wouldn't consider it sufficiently relevant to be disclosed.
Lots of Letby's legal team's decisions are confusing to me - like why they didn't call experts of their own? I've always thought that was a mad decision (unless the reality is that they couldn't get supportive experts, which tells its own story). Perhaps they felt their safest route was simply to attack the credibility or conclusions of the prosecution's experts, but if that was so, why not seek to have the investigation into Hindmarsh disclosed?
I can never really land on how I feel about this case. I generally trust the decisions of jurors who have sat through all evidence and arguments, but it's indisputable that miscarriages of justice do occur. I think the approach taken by Letby's team could be a case of legal advisors making the wrong call, or it could be a team doing their best in circumstances where the evidence is against them. I find Letby's behaviour around the families (keeping records, repeatedly looking people up online, the reports from colleagues of a kind of vicarious preying on intense emotion) to be highly suspect, but I'm wary of armchair psychology. It's a very uncomfortable one to sit with.