We've spent years covering the Lucy Letby case - here’s why experts are still arguing about it

There are 2 parallel universes successful the Lucy Letby story.

One tin beryllium witnessed each time successful Liverpool astatine the nationalist enquiry into her case. Here, the substance of Letby’s guilt is settled. The question for the justice is wherefore Letby was capable to harm babies for truthful long.

In the different universe, doubts astir the grounds utilized to convict her person been mounting. Leading statisticians and aesculapian experts are arguing Letby whitethorn beryllium the unfortunate of a miscarriage of justice.

It is simply a surreal authorities of affairs: a ineligible strategy that has decided Letby is simply a serial slayer - and a statement extracurricular that questions her guilt.

As journalists we person been covering the Lucy Letby lawsuit for years - done 2 trials, an appeals process, an ongoing nationalist enquiry and the increasing contention implicit her conviction. We person written a publication unneurotic and made 2 Panorama films astir the lawsuit - the latest of which airs connected Monday with caller information, and hears from some starring critics and the prosecution experts present nether fire.

Letby is officially the astir prolific kid slayer of modern times - convicted of murdering 7 babies and attempting to execution 7 others. And yet her lawsuit divides opinion.

Had idiosyncratic really seen her harming a babe astatine the neonatal portion successful the Countess of Chester Hospital, the lawsuit mightiness person been much straightforward, but no-one did. There was nary incriminating CCTV oregon DNA grounds either. The grounds against her was circumstantial.

One of the documents that played a cardinal relation successful her proceedings was a grid, listing the incidents successful the lawsuit with 'X's to amusement which members of unit had been connected duty. Letby was the lone caregiver connected work for each of them.

But the grid has attracted scorn from statisticians. They reason that we don’t cognize however the “suspicious events” listed connected the grid were selected oregon which incidents were excluded, truthful connected its ain the grid is small much than a ocular stunt. The assemblage besides heard determination were 2 suspicious incidents erstwhile Letby was not astatine enactment - neither of which was included connected the grid.

But is the grid truly the problem?

If determination was undisputed aesculapian grounds that 24 crimes had been committed, past surely the information Lucy Letby was contiguous each clip would beryllium damning.

And therein lies the cardinal question of the Letby case: How convincing is the aesculapian grounds that the babe deaths and collapses were decidedly crimes alternatively than people occurring events?

The astir arguable grounds acrophobic allegations that Letby murdered babies by injecting aerial into their blood. That would origin an aerial embolism - a blockage caused by an aerial bubble successful the humor circulation.

To bash this, Letby would person to person taken a syringe and injected the aerial into the babies’ intravenous lines. These are usually utilized to administer fluids, drugs, and nutrition to sick oregon premature newborns.

Syringes successful hospitals are thrown distant and incinerated aft they person been used. As a execution weapon, they are virtually untraceable.

The occupation is no-one saw Letby doing this. The allegation rested alternatively connected a “checklist” of observations of immoderate of the babies who died oregon collapsed portion Letby was around.

According to the prosecution, the babies deteriorated abruptly and unexpectedly. Retired advisor paediatrician Dr Dewi Evans was the prosecution's main aesculapian adept witness. He told us: “Babies don't abruptly driblet dead.”

Many exhibited unusual tegument discolourations that medics connected the portion hadn’t seen before. Some babies screamed.

The babies besides failed to respond to resuscitation arsenic medics expected. Post-mortem X-rays revealed aerial successful the humor vessels of some.

According to the prosecution, this checklist was a definite mode to place aerial embolism. But however robust was it? Research connected aerial embolism successful babies is precise constricted - thing the prosecution’s ain experts readily admitted.

One of the astir broad studies was a 1989 probe insubstantial by 2 Canadian academics. The relationship successful the insubstantial appeared to enactment the prosecution lawsuit - peculiarly its references to tegument colour changes associated with aerial embolism.

But the fig of cases successful the survey was constricted - conscionable 53 - and the circumstances of the babies described successful the insubstantial differed successful immoderate respects from those successful the Letby case.

Lucy Letby: Unanswered Questions

Reporter Judith Moritz, who has covered the lawsuit from the start, investigates the questions that person been raised astir Lucy Letby’s conviction.

Watch connected BBC iPlayer from 06:00 connected Monday 21 October - oregon connected BBC One astatine 20:00 (20:30 successful Wales and Northern Ireland).

One of the paper’s authors, Dr Shoo Lee, aboriginal appeared arsenic a witnesser successful Letby’s defence, during her unsuccessful effort to entreaty her convictions successful April 2024. He said nary of the tegument discolourations seen connected the babies successful the Letby lawsuit were impervious of aerial embolism.

Lawyers for the prosecution disagreed. They besides pointed retired that tegument discolouration was conscionable 1 point connected their aerial embolism checklist and that they had ne'er argued that 1 peculiar signifier of tegument discolouration was, connected its own, impervious of aerial embolism.

Several experts person publically criticised the prosecution’s aerial embolism theory, though hardly immoderate person seen each of the aesculapian evidence. One adept who has is the antheral who advised Letby's defence during her archetypal ten-month trial: retired advisor neonatologist Dr Mike Hall. Dr Hall didn’t really springiness grounds successful court, but helium told america that successful his presumption determination was nary impervious that the aerial seen successful the X-rays of the babies got determination portion they were alive.

These are the types of adept disputes present playing retired implicit the aesculapian grounds successful the Letby lawsuit - and immoderate of them person go personal.

Dr Hall believes determination were important flaws successful the prosecution’s aesculapian evidence.

He besides believes the prosecution experts overstated however unchangeable the babies were earlier they collapsed and died.

“Phrases specified arsenic the babe was really, truly good were fixed by the prosecution adept witnesses connected respective occasions for respective of the babies,” Dr Hall told us.

“And it was my presumption and is my presumption that they weren't really, truly well, they had signs of important illness.

“I deliberation that what the prosecution experts said was misleading for the jury. That’s not the aforesaid happening arsenic saying that they deliberately misled the jury.”

It is an allegation that some of the main prosecution experts cull emphatically.

Dr Dewi Evans told us: “Those suggestions are wholly flawed and bespeak either that the radical making them person not seen the objective grounds oregon that they are unaware of what constitutes well-being successful a premature baby.”

Consultant paediatrician Dr Sandie Bohin, the prosecution's different main expert, who is speaking astir the contention surrounding the lawsuit for the archetypal time, said: “I gave grounds nether oath 16 times. I told the truth.”

“It was my sentiment and remains my sentiment that these babies were unchangeable anterior to their collapse, truthful I can’t hold with those radical that suggested that I misrepresented the stableness of the babies and that I misled the jury.

“I deliberation that’s an outrageous suggestion.”

It is an denotation of the toxicity and aggravated part of sentiment successful the Letby lawsuit - adjacent among the experts.

One evident question is wherefore Dr Hall didn’t attest successful court. He intelligibly disagreed with the prosecution experts, and the information that helium didn’t springiness grounds meant that Letby had nary aesculapian adept witnesses successful her defence.

That has prompted immoderate to reason she didn’t person a just trial.

We asked Dr Hall if helium had been consenting to attest and helium said helium had.

He told america helium was expecting to springiness grounds and that helium was told of the determination not to telephone him “right astatine the past minute”- a determination that near him “at odds” with Letby’s defence team. Dr Hall told america helium was truthful acrophobic that helium adjacent considered penning to the justice to accidental helium believed that the assemblage had not heard the full truth.

But the eventual determination not to telephone Dr Hall arsenic a witnesser came from Letby herself – a constituent that Dr Hall acknowledges.

Why did she not telephone him? It is 1 of galore questions that lone she tin answer.

Letby was convicted of utilizing a assortment of methods to harm and execution babies - injecting aerial into their stomachs, force-feeding them with milk, dislodging breathing tubes, and inflicting trauma.

As with the allegations of aerial embolism, the prosecution relied heavy connected the opinions of experts to marque their case.

But determination was 1 portion of the prosecution’s statement that appeared to remainder connected thing much than idiosyncratic adept opinion: the insulin evidence.

Lab tests indicated that 2 babies had been poisoned. The basal rule progressive successful the trial was rather straightforward. When the assemblage produces insulin, it besides produces different substance called C-peptide, truthful C-peptide is simply a reliable marker of people produced insulin.

Although C-peptide is produced by the assemblage astatine the aforesaid complaint arsenic insulin, it clears overmuch much slowly. So you would typically expect to spot 5 to 10 times much C-peptide than insulin, if the insulin is natural.

Where you find precocious levels of insulin, but debased levels of C-peptide, determination is lone 1 evident conclusion: the insulin is not earthy and has alternatively been administered from the outside.

That is what investigators recovered successful 2 of the babies successful the Letby case. One had highly precocious levels of insulin successful his humor and a C-peptide level that was truthful debased that it was unmeasurable.

The 2nd babe had an insulin level much than 4 times higher than the C-peptide level, again indicating it had not been people produced.

The aesculapian information of the babies besides fitted with the laboratory results. In some cases, the babies’ humor sweetener levels had plummeted, which is what you would expect to spot with insulin poisoning. And portion no-one saw Letby poisoning either of the 2 babies, she was determination erstwhile they started experiencing symptoms.

Of each the allegations successful the case, this 1 looked similar the astir solid. In court, Letby herself accepted the technological grounds that the babies had been fixed unsafe quantities of insulin. She conscionable denied being responsible. Her lawyers were much cautious. They did not judge the insulin evidence, but they did not accidental it was incorrect either.

For the prosecution, the insulin grounds was cardinal to the full case. It seemed to beryllium that idiosyncratic connected the neonatal portion astatine the Countess of Chester Hospital was a poisoner.

If jurors could beryllium persuaded connected this point, it wouldn’t beryllium truthful hard for them to reason that Letby was the culprit.

And truthful they did. Of each the allegations successful the case, the assemblage returned unanimous verdicts of guilt connected conscionable 3 - and 2 of these were the insulin cases.

However, since then, sceptics person questioned whether the laboratory trial utilized to measurement insulin and C-peptide successful the Letby lawsuit was arsenic robust arsenic the prosecution had claimed. It is called an immunoassay test, and works by utilizing antibodies to observe and measurement substances.

Critics reason determination are circumstances successful which the trial tin mistake different substance for insulin. It is called interference and it could effect successful a mendacious positive. The critics accidental the lone mode to beryllium definite that the substance being measured is so insulin is to usage a much precise method of investigation - specified arsenic wide spectrometry.

We spent months examining this argument. Our conclusion, having spoken to starring experts connected each sides of this debate, is that, portion the immunoassay method is not perfect, it is usually close and the circumstances successful which interference mightiness hap are highly improbable successful the discourse of the babies successful the Letby case.

It is adjacent much improbable that 2 laboratory tests conducted wrong months of each different would some beryllium wrong.

In this week’s Panorama, we uncover caller grounds connected the insulin allegations and the question of whether Lucy Letby truly poisoned babies.

An enduring situation successful the Letby lawsuit - and reporting connected it - is the trouble of seeing the large picture.

Individual parts of the grounds can, and volition proceed to be, criticised. But it is not imaginable to scope a presumption connected the lawsuit without taking each of the grounds into relationship - and immoderate of this goes beyond the opinions of the aesculapian experts.

Letby’s clip successful the witnesser container was revealing for those who were there. During her archetypal trial, she spent 14 days being questioned. Several observers noted that she seemed aloof and indifferent. At times, she squirmed, and seemed to necktie herself successful knots.

She claimed she could not retrieve things - similar the decease of a babe she had texted colleagues about, oregon searching repeatedly for the parents of dormant babies online.

There are different details, not included successful Letby’s trials, that are besides challenging for the sceptics.

A full of 13 babies died successful the neonatal portion betwixt June 2015 and June 2016. Letby was connected work for 12 of them.

And yet, no-one really saw her harm a baby.

In caller weeks, respective of Letby’s colleagues person fixed grounds to the Thirlwall Inquiry saying that they person since travel to realise her guilt.

However, erstwhile consultants began to fishy her backmost successful 2016, galore of her nursing colleagues remained fiercely loyal – and they remained loyal adjacent aft her removal from the neonatal portion successful July 2016.

It’s not hard to recognize why. There is thing evident successful Letby’s inheritance that points to her becoming a killer. Her parents look to person adored her, and her relationship groups successful Hereford - and aboriginal successful Chester - were blessed and supportive. Her closest friends successful Hereford stay convinced she is innocent.

Then determination is Letby’s ain continued protestation of innocence. In July 2024, she was convicted of a further number of attempted murder. After proceeding the verdict, earlier being taken to the cells, she turned to the justice with outstretched palms and said: “I’m innocent.”

Letby present has a caller lawyer, Mark McDonald, who plans to instrumentality her lawsuit to the Criminal Cases Review Commission (CCRC). Her attempts to entreaty against her convictions person truthful acold failed.

Mr McDonald tells america helium has gathered the finest experts successful the satellite to reappraisal the prosecution’s aesculapian and technological evidence. He says the prosecution’s lawsuit was flawed and helium is assured his squad of experts volition springiness him the arguments helium needs to situation her convictions.

But the CCRC process could instrumentality years. In the meantime, battles implicit the grounds volition continue. That means much heartbreak for the families of the babies, who accidental they find the continual questioning of Lucy Letby’s convictions “grossly violative and distressing”.