One of the big dangers of letting the use if medical evidence go unchallenged in this case is the danger of precedence.
Medical dogma is already used in the family courts to determine child abuse "on the balance if probabilities" - such things as metaphyseal fractures, considered pathognomic of child abuse, shaken baby syndrome, and MSBP / FII. When these things occur in babies, it is almost impossible to prove it's not abuse as chances are there are no witnesses. Often parents present bewildered in hospital with a baby with symptoms and are then blindsided by an accusation that can lead to a child being removed for permanent adoption. Often it doesn't come to a criminal trial because it is based on expert opinion and the barest of circumstantial evidence, ie X was the person alone most often with the child, ergo, X is the perpetrator. Even if it does, a not guilty finding is no guarantee you get your child back. Also, discovery of an underlying condition ironically may mean you are more likely to have abused your child, as medically vulnerable children are statistically (allegedly) at higher risk of abuse.
So, moving forward, if the evidence in Lucy Letbys case isn't looked at, potentially every time a baby dies in similar circumstances in hospital, the idea has been planted "ooh, I bet it's air embolism" or "is it insulin poisoning?" and by extension all the staff then fall under suspicion. There's a danger of it becoming the diagnosis de jour, much like FII allegedly spiked after Salky Clark and Angela Cannings.
FII as a motivation is a fantastically convenient way to hide iatrogenic abuse or error, or to provide a "motive" in caregivers. If you deny you have it - that's a signifier of the condition. Spotting the early signs often occurs when a mother challenges a professional over their care, conveniently.
So, getting this case thoroughly overhauled is in the best interests of everyone - you, me, medical professionals, children and the judiciary. Otherwise the danger is a case like this every time there's an allegedly unexplained health episode with a child.
And the criticism may come that these controversial child abuse diagnoses are the last resort when everything else has been ruled out. Unfortunately not so. A request for a collagen test, done by biopsy can be posited as evidence if further child abuse if your child has metaphyseal fractures, for example. I have direct experience of this.
I know some people abuse and kill children and wish to see them protected. However, what starts out as a vague theory can be a meal ticket for a high flier medic who sees everything through their own narrow lens.
Air embolism cannot be allowed to become yet another convenient go to in complex medicolegal cases when the evidence for it appears to be so extremely contentious.