Last year, Letby faced one of the longest murder trials in British history. The police had spent six years gathering evidence after multiple babies died in the neonatal unit where Letby worked. Evidence from both sides was presented in painstaking detail. The trial jury couldn't reach a unanimous verdict, so a retrial followed. In the end, it was the prosecution's case that sealed the judge's decision for life imprisonment. The jury couldn't reach a unanimous verdict on a few counts. Thus, the case against Letby was extensive, with volumes of evidence painstakingly sifted through over many months.
Letby's house contained notes that seemed to confess her evil nature. One note simply stated, "I am evil." On social media, Letby frequently searched for the families of the babies who had died. The prosecution argued that these were not normal behavior and that they powerfully evidenced her guilt. ... But the crux of the prosecution's argument was that, at least in some cases, Letby had poisoned the babies using a method that insured they would become dangerously hypoglycemic. ... Hypoglycemia on its own poses a serious threat to life and health. When coupled with the doses of insulin that were found in the babies' bodies and the factors that indicated a probable use of a syringe, the charge was a powerful one.
Forensic toxicology expert Prof. Alan Wayne Jones noted that the tests used on the babies measured not the actual substance but the body's reaction to it, which in this case could mean the babies' bodies were reacting to insulin they or their bodies had created. Jones further stated that if there was any suspicion that the babies had been given synthetic insulin, the testing lab was required to ship the samples to a specialist centre for confirmation. The "normal" tests wouldn't give reliable enough results to use them in the way the clinicians did.
The testing lab’s own website states that if synthetic insulin is suspected, the results should be verified externally by a specialist centre. Clinicians at the Countess of Chester did not do that because both babies recovered.
"The problem is that the method of analysis used [in these two cases] was probably perfectly good from a clinical point of view, but not a forensic toxicology point of view," he said.
"That test cannot differentiate between synthetic insulin and insulin produced by the pancreas."
No one is disputing the fact that the babies suffered from sharp drops in blood sugar levels... or that those drops might have been the result of something that Letby did to them. But as Jones pointed out, there are other possible explanations for those events. And when you look at what those other explanations are, they seem at least as plausible as the idea that Letby, in particular, was committing murder, and that she was doing so in a way, a method, that is not known to have been used by any other babykiller before her.
The prosecution cited a 1989 paper by Canadian neonatologist Dr. Shoo Lee on the phenomenon in question. That paper described, as an indicator of air embolism, a distinctive rash of bright pink blood vessels against blue skin. In April, at Letby's Court of Appeal hearing, Dr. Lee testified for the defense. The defense claimed he was outlining a distinctive rash that did not appear to be consistent with what witnesses had described for Letby's case.
At the preliminary trial, Dr. Lee did not testify; the defense did not utilize any expert witnesses; and the only witnesses to testify for the defense were Letby and the plumbing expert. However, the prosecution had the advantage of calling six expert witnesses to the stand. One of the main witnesses for the prosecution was Dr. Dewi Evans. He is a former pediatric consultant and has decades of experience testifying as an expert witness. Evans's testimony was pivotal to the case against Letby.
He stated that he had reviewed a total of 18 research articles on air embolism, which went far beyond the consultative opinion of Dr. Lee. This witness was so certain that what he had observed in this case was valid that not only did he say it in his own voice, but he also had two other specialists say it for him: a radiologist and a neonatal pathologist.
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