There has been a tendency in cases of infant death, specifically those concerning non-accidental head injury, for appellants to seek exoneration from their conviction through the sourcing of new witnesses, who can present evidence not encountered at the time of the trial. In order to effectively assess the potential pitfalls necessary to avoid a dismissal on appeal it might be beneficial to look to other cases concerning the death of infants under the care of an adult. The legal complexities and challenges associated with cases involving allegations of shaken baby syndrome (SBS), appear to have significant overlap with those challenges that Letby's team may face in mounting her appeal. Such cases often involve the death of an infant under the care of an adult, where the cause of death is difficult to determine due to the lack of testimony from the child, as a result almost all the evidence available is reliant, if not heavily so, on expert medical evidence.
As with the Letby case, SBS cases are inherently complex due to the tragic nature of a baby's death under the care of an adult, usually a parent or childminder. The absence of direct testimony from the victim (the baby) means that experts, prosecutors, and juries must piece together what happened. The challenge lies in the temptation to find a definitive cause for the child's injuries, especially when expert evidence points towards non-accidental harm and there is no apparent alternative explanation. Even though there is a notion that the wisdom of science requires that the court's directions to the jury be faithfully upheld this may not actually be reliably followed. This is especially the case where there is an inherent temptation to deny the very real possibility that the true cause of death may remain unknown even after extensive examination.
In the case of Lucy Letby, it was widely suggested that the failure to present a defence was her downfall, however, there is another reality here that was not appropriately explored in the wake of her conviction. The defence did retain an expert witness, Dr Michael Hall, a retired neonatologist who holds a visiting professorship at Southampton University, and was a reviewer of the Ockenden Report. Dr Hall even took the time, during the trial to write to the BMJ in response to one of many published articles on air embolism, pointing out certain inconsistencies with the terminology used. It is unfortunate that Dr Hall failed to focus in any meaningful way on the 2015 study into air embolism in premature infants due to CPR, as this review in of itself was much more fitting for the case (See Halbertsma et al., 2015).
Did the Expert Witnesses on either side meet the grounds established in the Kennedy Review?
Perhaps what has gone forgotten in the trial of Lucy Letby was a report commissioned nearly twenty years ago titled: "Sudden Unexpected Death in Infancy: The Report of a Working Group Convened by the Royal College of Pathologists and The Royal College of Paediatrics and Child Health." The chair of the working group was Baroness Kennedy KC, and the finalized report was published in September 2004. The Kennedy Review issued a clear caution against doctors using the courtroom to "fly their personal kites or push a theory from the far end of the medical spectrum". Though more relevant for Letby's case were Baroness Kennedy's recommendations for the trial judge before expert evidence is admitted, including:-
Is the proposed expert still in practice?
To what extent is he an expert in the subject to which he testifies?
When did he last see a case in his own clinical practice?
To what extent is his view widely held?"
None of these questions can be answered in a positive light for either the prosecution expert witnesses nor the defence expert witnesses. Whether the failure to meet the above grounds could be challenged at so late a stage, where a jury has already been invited to determine innocence or guilt, is another matter. Nevertheless, in the analysis of three appeals concerning convictions for SBS, [R v Henderson; R v Butler: R v Oyediran 2 Cr App R 24] the Court of Appeal reflected that the failure of a medical doctor to be in clinical practice at the time he undertakes the work of an expert is highly problematic. The Court summarized that there could be issues where an expert is a retired medic, no longer in clinical practice. What is most curious is the Court's failure to recognise the actual diagnostic error rate in clinical medicine, and the fact that clinical medicine cannot actually be used in place of forensic science.
In regard to the Letby case, the court was not definitive on the requirement of practicing medics, and given that the defence expert witness was also retired from practice, one wonders whether there is any precedent for a legal team to declare to the court that they engaged in the same errors that were performed by the prosecution witnesses. Still, the opinion is relevant in that it may give some explanation as to why the Letby case proceeded under a canopy of speculation, which never rose to any thing close to evidence:
"Such clinical experience..., may provide a far more reliable source of evidence than that provided by those who have ceased to practise their expertise in a continuing clinical setting and have retired from such practice. Such experts are, usually, engaged only in reviewing the opinions of others. They have hlost the opportunity, day by day, to learn and develop from continuing experience."
It may just be that when one is not actually in practice, and where one has no real investigative or research background, it becomes much easier to speculate on the cause of the collapse of numerous babies, and advance hypotheses that one cannot back up with actual first hand experience. Dr Sandra Bohin, reportedly only witnessed one case of air embolism in her entire career, and Dr Dewi Evans freely admitted that he had not ever witnessed phenomena he reported on:
"If you inject the large volume of fluid or fluid and air into the stomach, the stomach becomes distended. This makes it more difficult for the baby to breathe. Because the diaphragm is unable to move up and down, and you will get a sudden deterioration. And this is something I've never seen before and never seen since. But that was a condition that was easier to prove." Dr Dewi Evans, September 2023
New Evidence is not the same as New Experts
It is reasonable to assume that Letby might, as has been attempted in cases of SBS, seek to present evidence from a new expert witness in her appeal. Whereas such an approach seems obvious and may on the surface expose further inadequacies in the prosecution's case, there is a stark reality that a new expert witness does not equate to new evidence. One can identify this tendency to assume that a change in medical doctor along with their expert opinion is sufficient to overcome the evidence that secured the appellant's conviction. Before Letby seeks to rely on this assumption it might be worthwhile to review the manner by which the court responded in R v. Henderson , a case where a highly praised child-minder was convicted of murdering a baby under her care by allegedly shaking the 11-month old to death. In Henderson, the appellant sought to challenge the prosecution evidence presented at the trial through the admission of fresh evidence pursuant to s.23 of the Criminal Appeal Act 1968.
The CoA has been reticient to accept challenges by way of the admission of fresh evidence where that evidence is essentially an additional opinion of an expert witness who was otherwise available at the time of the original trial. This point was emphasized by Lord Bingham CJ in R v. Stephen Jones  1 Cr App R 86, and further affirmed by Sir Anthony May P in R v Meechan EWCA Crim 1701. In both instances it was made clear that it would subvert the trial process if a defendant were to be generally free to mount on appeal an expert case which, if sound, could and should have been advanced before the jury to rebut claims made at trial. Likewise, in R v Kai-Whitewind  2 Cr App R 31, the Court of Appeal observed that only in the rarest of circumstances should an appellant be permitted to offer a repetition or near-repetition of "evidence of the same effect by some other expert" as a basis for appeal. In essence, there is consensus that hearings of appeals should not be permitted to present an opportunity to call new experts in the hope that they might do better than those whose evidence had previously been rejected.
Of particular concern is the CoA's view of an appellant's use of new expert witnesses who were of a similar professional background to defence experts, who were used at trial but not called to testify. In Henderson, the CoA took a dim view of the use of the same type of expert witness in an effort to put new evidence before the court at appeal:
“The fresh evidence was, in substance, not fresh evidence at all. The witnesses were "fresh", their evidence was not. It was evidence from experts in the same disciplines as those whose reports the defence had previously obtained but decided not to call. The appellant's previous representatives had chosen not to call the expert evidence because it helped the prosecution. That was a choice within the bounds of reasonable decision. If they had called that evidence and the jury had convicted, they would, probably, not have been permitted to adduce further evidence from experts in the same disciplines. They should not be in a better position because of a previous, sensible choice not to call the experts.” R v Henderson 
Further summarizing their procedural difficulties relating to new expert testimony, the CoA affirmed that even where the charge of murder appeared incongruent with the defendant's background and reported reputation, the failure to present novel findings, by experts who were of an expertise, distinct from the defence expert witness at trial, was insufficient for the conviction to be deemed unsafe.
"We cannot substitute, for the jury's verdict, a conclusion based upon perplexity as to how this appellant could have treated [the baby] with unlawful force, even momentarily. That was an issue which the jury resolved.”
The need to Identify New Evidence that is identified by Novel Experts
It remains, as with the air embolism claims put forth by the prosecution expert witnesses, that the science in the SBS cases is just as poorly contrived and peculiarly accepted as "scientific evidence" by English Courts. Reviewing opinions from the CoA is illuminating as it provides an insight to the extent by which medical doctors have so clearly convinced the legal profession that their medical knowledge equates to scientific validity, and even in the face of scores of scientific research, their opinion should override peer reviewed empirical evidence.
In the case of Henderson, much focus was placed on the fact that doctors determined the infant exhibited retinal haemorrhages, one of the three diagnostic symptoms associated with the increasingly tenuous "triad" associated with SBS. It is now widely understood that retinal hemorrhages that are “dense, extensive, covering a large surface area, and/or extending to the ora serrata” occur relatively commonly in cases of head injury unrelated to abuse or shaking. There is a now a growing body of research demonstrating that severe retinal haemorrhages have myriad antecedents in infants. The primary corrrelate with intensity of retinal haemorrhages is reportedly the extent of the intracranial pathology, thus the more severe the neurological complications, the more likely the presence of retinal haemorrhages.
In support of the lack of reliability of the expert witness testimony in SBS cases a recent study sought to determine the diagnostic error associated with medical doctors making a determination of abusive head trauma in children under the age of 3 years old. Brook (2023) relied on data from the the Pediatric Brain Injury Research Network (pediBIRN) database, focusing on patients under three years old who demonstrated acute symptoms of head injury. The study aimed to compare cases of abusive head trauma (AHT) with those due to witnessed accidental head inury (non-AHT) in infants. The study utilized events that were independently witnessed as a benchmark to determine the frequency of misdiagnosing non-AHT incidents as AHT, and to identify the risk factors contributing to this misdiagnosis of AHT/SBS by medical professionals.
The study reveals that accidents are frequently misdiagnosed as abusive head trauma (AHT), especially in the presence of acute encephalopathy, bilateral or interhemispheric subdural haemorrhage (SDH), and/or severe retinal haemorrhage (RH). The likelihood of misdiagnosing accidents as AHT increases sharply as the severity of intracranial pathological conditions intensifies. Despite statistical differences in the findings of witnessed non-AHT cases versus diagnosed AHT cases, misdiagnoses still occur, moreover the symptoms in non-AHT cases can overlap with those used by physicians to diagnose abuse, leading to a significant risk of misdiagnosis.
Furthermore, the misdiagnosis of undiagnosed or unknown medical conditions, or evidence supporting alternative explanations for symptoms typically associated with AHT, suggests that the actual rate of misdiagnosis could be even higher than currently recognized. This includes both misdiagnosed non-AHT cases and cases where other causes for AHT-like symptoms are present.
Turning to an actual assessment of the diagnostic error rate, describing those events that medical doctors incorrectly diagnose as abusive head trauma/Shaken Baby Syndrome/non-accidental head injury it was found that out of 100 witnessed non-abusive head trauma (non-AHT) cases, 14 have been incorrectly diagnosed as AHT. This indicates that, according to this reference standard, approximately 14% of accidental cases are wrongly identified as abusive head trauma. We could therefore posit that this diagnostic error rate would be reflected in convictions for AHT/SBS. Further, owing to the focus on the medical criteria, which is increasingly viewed as non-specific for SBS/AHT, that there can be no actual evidence presented to the court to refute the findings made by expert witnesses, as those findings are not matters for debate. Rather, the interpretation of the findings is what these cases turn on.
In Henderson, during the trial, the defense presented Dr. Anslow, a Consultant Paediatric Neuroradiologist, as their expert witness. Dr. Anslow suggested that the baby might have experienced a spontaneous seizure leading to hypoxic-ischemic brain damage, which could cause brain swelling and increased intra-cranial pressure. However, the defense did not contest the presence of the triad (widespread bilateral retinal haemorrhages, thin film subdural haemorrhage, and encephalopathy), retinal folds, and axonal damage, nor the assertion that these signs indicated violent trauma. Dr. Anslow's expertise did not cover the issues of retinal folds and axonal damage. Consequently, the appellant could not account for these two critical aspects, in addition to the triad, which were central to the prosecution's case. Henderson's appeal revolved around her efforts to address the two additional criteria alongside the triad. When considering Letby's case we might imagine a similar approach could be undertaken, that is she may seek to challenge those matters that were not effectively tackled during the trial. Though to do this it will require that she do significantly more than seek out the same type of expert witness she failed to use at her trial.
Henderson lost her case on her appeal, as it was concluded that the finding of retinoschisis (retinal folds) was a clearly unique feature attributed to SBS/AHT, in actual fact this physiological abnormality commonly occurs in non-abusive head trauma. With regard to the axonal damage, it is anyone's guess why this was ever tolerated as validation of SBS/AHT. In the original studies defining SBS/AHT axonal damage was a rare event and was present in only 3 out of 53 children (Geddes et al., 2001). In the case of Henderson, what is clear is that instead of thoroughly investigating the clinical and post-mortem records of the infant, there was an effort to rebut the claims made by the prosecution. There is only one way in which one can approach such a crass assault on a medical hypothesis, and that is to develop an evaluative inference based on one's subjective knowledge. Such an approach is apparently doomed to failure in the CoA. It appears that the only way to overcome such an approach is to develop a robust scientifically valid evaluation of the case.
It is 2023, there exist over 1008 peer reviewed articles on SBS alone, when one searches these key terms in PubMed, a search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. To take an approach to rebutting medical claims made by an assortment of doctors, which were used to secure a conviction for serial murder, which essentially sets out to rebut an opinion of another medical doctor, is a deeply flawed approach. Indeed, this approach is so limited in its viability that the Court of Appeal and the very underpinnings of scientific reason are actually in a state of alignment, albeit for different reasons.
Still, there is much speculation as to the basis of Letby's ongoing appeal, what seems very clear is that in the event she seeks to submit as new evidence, the opinion of a similar expert witness to the one she failed to use at the trial, she may find that this approach has the opposite effect to which she intended. Instead of raising doubt as to the veracity of the prosecution experts, it may send a message to the Court of Appeal that she is seeking a second bite at the apple. One cannot tackle a case with the scientific complexity observed in that of Letby's case without taking an investigation into the cause of death of the infants. Anything less than that is not only wholly unscientific, it is also unnecessarily limiting, as it forces the appeal to be based on only that which the prosecution alleged, and forgoes any opportunity to identify new evidence, which is independent of the medical opinion of prosecution experts.
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Acta Neurol. Belg., 117 (2) (2017 Jun), pp. 515-522, 10.1007/s13760-017-0748-0
R v Meechan EWCA Crim 1701
R v Kai-Whitewind  2 Cr App R 31
R v. Stephen Jones  1 Cr App R 86
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