LUCY LETBY, a neonatal nurse at the Countess of Chester Hospital, was charged in November 2020 with seven counts of murder and 15 counts of attempted murder in relation to 17 babies at the hospital. Having been convicted by two separate juries, she is now serving 15 whole life sentences.

In February, the veteran Conservative MP Sir David Davis described her convictions as “one of the major injustices of modern times,” and Sir Jeremy Hunt has called for an “urgent re-examination” of the case.

A number of medical specialists believe that the expert evidence was unreliable. Letby herself has called for a halt to the public inquiry into her crimes, arguing there is now “overwhelming and compelling” evidence which undermines the convictions. Her case is supported by a “Free Lucy” website and in Private Eye.

There have been catastrophic miscarriages of justice in the past, the most infamous being that of Timothy Evans. He was hanged in 1950 for the murder of his daughter at 10 Rillington Place. Evans had difficulty learning to speak and may have had a learning disability. His downstairs neighbour, John Christie, was a key witness in his prosecution and conviction. After Evans’s death, it emerged that Christie was a serial killer who had murdered several other women in the same house.

A case which was often coupled by campaigners with that of Evans was the execution in 1962 of James Hanratty, known as “the A6 murderer.” He was convicted of shooting dead Michael Gregsten in a car at Deadman’s Hill in Bedfordshire. It was alleged that he also raped Gregsten’s girlfriend, Valerie Storie, shot her five times and left her paralysed. The prosecution’s case was based on her identification of Hanratty at an identification parade.

For several decades, Ludovic Kennedy protested his innocence in articles, Paul Foot campaigned in Private Eye for a pardon, and the Hanratty family repeatedly called for further inquiries. In 2001, his body was exhumed and his DNA compared with DNA extracted from a handkerchief and underwear worn by Storie. The DNA samples from both sources exactly matched Hanratty’s DNA.

Taken together, the two cases demonstrate that not only the justice system but also legal campaigners are capable of errors of judgement. It is also true that senior judges and the Criminal Cases Review Commission (CCRC) have not always been sufficiently open to the need to review or set aside unsafe convictions.

Earlier this year, the chairperson and chief executive of the CCRC resigned as a result of the commission’s failings in the case of Andrew Malkinson. His case was twice rejected by the CCRC, and he spent 17 years in prison for a rape he did not commit.

The record of our judges is much improved, but was highly unsatisfactory in the not-too-distant past. The convictions of the Guildford Four (1974), Birmingham Six (1975) and Maguire Seven (1976) were only quashed after the innocent men had spent many years in prison. Along the way, the conduct of senior British judges — including two Masters of the Rolls, Lord Donaldson and Lord Denning — was rightly criticised.

People disagree about what constitutes a “miscarriage of justice.” In 2011, the Supreme Court held that it occurs “when a new or newly discovered fact shows conclusively that the evidence against a defendant has been so undermined that no conviction could possibly be based upon it.”

Whereas civil cases are decided by our courts on the “balance of probabilities” (ie, on a more likely true than not basis), guilt in a criminal court must be established “beyond reasonable doubt.” The court must be “sure.” This means that every week, many people are acquitted who, on the evidence, more likely than not committed the crime with which they are charged.

In one sense, and particularly from the viewpoint of the alleged victim, such cases are miscarriages of justice. Indeed, Tony Blair said in June 2002 that “it’s perhaps the biggest miscarriage of justice in today’s system when the guilty walk away unpunished.”

Acquitted citizens are, however, entitled to be treated as innocent of the charges against them. There is no “not proven” verdict of the kind found in Scottish law, and our system — rightly in my view — subscribes to “Blackstone’s ratio” that it is better that 10 guilty persons escape than that one innocent person is condemned.

The fact that our criminal law system is deliberately weighted in the defendant’s favour means that it will be rare for a defendant to be convicted in the Crown Court against the weight of the evidence.

However, certain factors do increase the risk of an unsafe conviction: pronounced public hostility towards the accused in a notorious case; irresponsible press coverage; trial by social media; a suspect’s vulnerability; eyewitness misidentification; inadequate defence representation, often caused by legal aid cuts; dogmatic prosecution experts; failure to disclose vital evidence; evidence contamination and faulty forensic analysis.

What to make of the campaign in support of Letby? There are reasons to take a cautious approach. The first jury sat for 10 months. It convicted her of some but not all charges and could not agree a verdict on others; that indicates it carefully considered the evidence against her on each count.

It is unlikely that most campaigners, commentators and outside experts were present in court each day or have read all of the expert evidence, witness statements and trial transcripts. A criminal trial is a careful forensic process, trial by social media and newspaper summaries are not. Guilt and innocence cannot reliably be assessed by people with only partial access to the evidence. One must, in particular, be sceptical of conspiracy theories.

The Court of Appeal’s decision on July 2 2024, refusing leave to appeal after a three-day hearing, is set out in a carefully reasoned decision that is 58 pages long. In essence, between June 2015 and June 2016, there was a significant rise in the number of deaths and sudden and serious collapses of babies at the hospital unit for no apparent reason. The probability of the unit recording eight deaths a year, given its previous mortality rate was 0.008, is very low.

Several deaths occurred in infants who were previously stable and whose collapse was sudden and unexpected. Some of the treating doctors observed that they had seen nothing like it before or since. It was later established that two or three bags of baby drip feed had been spiked with synthetic insulin.

Letby alone was present on the unit at the time of all of the deteriorations and deaths, and was the common factor in all of the cases. She was standing by Baby A’s cot at the time of the collapse and attended Baby B 14 minutes before the monitoring alarm sounded, although the baby was not her patient.

She took home and hid under her bed over 200 confidential handover sheets and had at home a handwritten note which included statements such as, “I am evil, I did this” and “I killed them on purpose because I’m not good enough.”

The causes of death were various (but bear some resemblance to the case of nurse Beverly Allitt, who injected air into babies’ bloodstreams and overdosed them with insulin at Grantham and Kesteven Hospital in 1991): air embolus; acute bleeding; insulin poisoning; overfeeding with milk; throat trauma; and traumatic liver injury.

Although campaigners have criticised the quality of the expert evidence, in particular that of Dr Evans, Letby herself accepted that two babies were poisoned with insulin, while denying she was the poisoner.

The prosecution had all of the neonatal patient records reviewed by a retired consultant paediatrician (Dr Evans), whose conclusions were then peer reviewed by a practising consultant neonatologist (Dr Bohin).

It commissioned additional expert reports from a forensic pathologist and histopathologist; a consultant paediatric radiologist; a consultant paediatric haematologist; a consultant paediatric endocrinologist; a consultant paediatric neuroradiologist; and a consultant paediatric surgeon.

The overall effect, according to the prosecution, was that natural causes were not a credible explanation. The jury accepted this. Although Letby instructed several experts of her own pre-trial, the defence declined to call any of them to give evidence contradicting or qualifying the opinions of the prosecution experts.

The Court of Appeal found that the trial judge “handled the trial with exemplary skill and patience.” It has twice refused Letby permission to appeal. This indicates that the appellate court was satisfied that the trial process was fair and the jury’s verdict open to it based on sufficiently reliable evidence.

Although some outside experts now proffer alternative explanations of some deaths and the significance of Letby’s note, it is always the case with a ten-month trial that individual pieces of evidence can be interpreted in more than one way. A jury makes its decision on the totality of the evidence.

The current position is therefore that two properly directed juries heard and considered all of the evidence put before them and were sure — satisfied beyond reasonable doubt — that Letby was guilty of some of the charges against her. If the convictions are unsafe and to be set aside, it must be on the basis of compelling new evidence.

As to this, the defence attempted in the Court of Appeal to adduce new expert evidence from Dr Shoo Lee, a neonatologist. His evidence, it was said, demonstrated that Dr Evans and Dr Bohin wrongly used skin discolouration as a means of diagnosing air embolus.

However, as the court pointed out, no prosecution expert diagnosed air embolus solely on the basis of skin discolouration. The verdicts were based on all of the evidence, not on isolated facts or expert opinions considered separately from the case as a whole.

The CCRC and, if the case is re-referred, the Court of Appeal, must keep an open mind and fairly assess any new evidence filed on Letby’s behalf. However, at present, the Court of Appeal’s analysis seems to be well-reasoned and fair.

Anselm Eldergill was a judge in the Court of Protection until 2024. He is a solicitor, an honorary professor of law and an academic associate at Doughty Street Chambers.