Dressed in her blue nursing uniform with her name badge pinned proudly on her chest, the young, blonde girl in her mid-20s is now the UK's most notorious child killer.

Described as non-descript and normal by police, few could envisage the horror she would inflict on innocent families.

Born in Hereford on 4 January 1990, Letby is the only child of John and Susan Letby, a retail boss and accounts clerk who are now both retired.

After attending a local school and sixth-form college, Letby qualified as a children's nurse at the University of Chester in 2011.

She completed training placements in Liverpool Women's Hospital before joining the neonatal unit at the Countess of Chester Hospital on 2 January 2012, just two days before her 22nd birthday.

Her life at this point was extraordinarily normal.

She lived in several houses, before buying her suburban, red-brick, semi-detached home in 2016 which was around a 20-minute walk from the ward.

An ornate teal bird feeder had been put up on the wall of the porch with a simple, child-like decor throughout the house.

In her bedroom, fluffy toys were laid across a duvet inscribed with the words "sweet dreams". Artwork saying "leave sparkles wherever you go" was pinned to the wall, illuminated by twinkling fairy lights.

Told colleagues she was bored

Letby owned two cats, Tigger and Smudge, and was close with her parents, saying in messages she felt "guilty" for not visiting them more often.

She had friends and an active social life, holidaying in Ibiza, going on nights out and attending weekly salsa dancing classes.

Letby used social media regularly to keep in contact with colleagues, friends and family and even exchanged messages with management on the neonatal ward.

At work, she was trusted and dedicated, having completed specialist training in March 2014 and regularly working in what was called nursery one - where the most ill children were cared for.

It was known as the "hot room" - an average-looking room with yellow walls alongside paintings of owls and teddy bears.

She would text colleagues when working in the lower-risk nurseries - two, three and four - that she was bored and wanted to work in nursery one - which the prosecution later said was a trigger for Letby to carry out attacks.

Follow live from court - Anger as Letby expected to skip sentencing

'Beige or vanilla'

It was speculated that Letby had a romantic crush on a married doctor on the ward, having exchanged hundreds of messages with him. The pair had also gone out for meals, been on a trip to London together and spent time at her home.

But while the details of her life may seem banal, the Crown Prosecution Service alleged there was a "much darker side to her personality". A member of the prosecution team described her as "devious, calculated and cold-blooded".

"There isn't anything outstanding or outrageous about her. She was a normal, 20-something-year-old," DCI Nicola Evans from Cheshire Police said.

"She had a normal job, she was average in that job, she had a group of friends and a family and a social life, nothing that you wouldn't expect from someone of her age at that time.

"The fact she was non-descript and average in work allowed her to go under the radar and commit these offences.

"There wasn't anything outrageous about her, there wasn't anything that stood out about her, she was beige or vanilla. She was present but not featured."

The start of the attacks

Letby had worked at the Countess of Chester hospital for more than three years when the mortality rate of the neonatal unit began to rise in 2015.

Her first attack came on 8 June 2015 when Child A died less than 90 minutes into Letby's overnight shift.

Letby used several methods to kill or severely injure the helpless victims - including physical assaults, overfeeding with milk, forcing air into their stomachs, and injecting air into their bloodstreams.

Two victims survived after Letby poisoned their IV drip bags with insulin.

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The prosecution accused Letby of varying her methods to avoid detection.

Some babies were subjected to repeated attempts by her to kill them.

The jury heard Letby would use medicines and equipment readily available to her to cause babies to unexpectedly collapse across day and night shifts.

Her victims included both boys and girls, many of whom were born prematurely.

After she had killed the infants, Letby searched for 11 of the victims' families on social media and even sent one set of parents a sympathy card on the day of their baby's funeral. She took a photo of the sympathy card before she posted it.

Letby was said to be relaxed and collected despite the rising number of deaths.

The parents of Child L and M - twin brothers who were just days old when Letby tried to kill them in April 2016 - said she was acting "very cool and calm" after she injected Child M with an injection of excessive air.

But Child M survived, after which "her body language and her behaviour totally changed", the twins' mother said.

"She was very annoyed with us. She thought that 'I couldn't kill your baby'."

She also made unusual comments which aroused suspicion at this time.

As Child P was being readied to be moved to another hospital in June 2016 after Letby pumped excess air into his stomach, she said: "He's not leaving here alive, is he?"

She had made a similar remark when Child C fatally collapsed a year earlier.

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Letby was accused of committing the murders in a one-year period - between June 2015 and June 2016 - out of her five-year career.

But Cheshire Police said it is investigating whether Letby could be responsible for any further attacks before June 2015, both at Countess of Chester Hospital and Liverpool Women's Hospital.

As part of that probe, they are reviewing the care of around 4,000 babies in the two hospitals.

'I am evil'

On the surface, there is no rhyme or reason to Letby's attacks, and she has offered no motive for her crimes.

She stuffed reams of confidential medical paperwork in reusable shopping bags, with some of these notes concerning the babies who had been killed or injured.

Letby scribbled all kinds of messages but on some she had written: "I am evil", "I did this" and "I don't deserve to be here because I'm evil".

Prosecutors said the notes illustrated a woman in turmoil, grappling with the guilt of her actions.

But Dr Sohom Das, a consultant forensic psychiatrist, said Letby doesn't fit any "typical" killer profiles.

'Low self-esteem and self confidence'

He says women who kill babies are usually driven by psychotic beliefs.

"I've seen at least two or three patients who have had delusional beliefs related to schizophrenia, for example, where they believe children are marked by the devil, that they're somehow saving them from hell or damnation," he told Sky News.

"Letby doesn't fit into that category. I've also met serial killers and they tend to be antisocial, angry, they tend to have a long criminal history of violence. Again, Letby doesn't fit that kind of motivation."

Beatrice Yorker, a professor emerita of nursing and criminal justice and criminalistics at California State University in Los Angeles, said Letby also does not fit the profile of an attention-seeking killer like Angel of Death nurse Beverley Allitt.

"I haven't read anything about Lucy Letby that indicates she wanted to be the centre of attention, that she enjoyed resuscitation of the infants. She seemed much more clandestine and deceitful. Kind of sadistic, maybe."

Dr Das said Letby suffered from low self-esteem and self-confidence which may have manifested a degree of jealousy.

'The most cowardly act'

In one note, Letby wrote she had an "overwhelming fear... I'll never have children or marry... I will never know what it's like to have a family... despair".

Dr Jane Carter Woodrow, a screenwriter and member of the British Society of Criminology who has written several books about murderers and serial killers, said it is likely Letby may fit the profile of a psychopath.

The NHS defines a psychopath as someone with an antisocial personality disorder meaning they are manipulative, lack empathy, and often have a total disregard for the consequences of their actions.

"How could she not be [a psychopath] to be able to do those things," she said. "It's the most cowardly act of all killers, [to kill] a child or an elderly person."

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'Trust me, I'm a nurse'

Dr Carter Woodrow says that "once you've crossed that line" and "murdered for the first time, I think it gets easier. And you see she feels emboldened as time goes on and the cases kind of escalate, particularly towards the end".

The fact Letby pleaded not guilty also shows psychopathic traits, she says. "She could have pleaded guilty and not put the parents through this terrible trauma again. She could have spared them all these details they've had to sit through."

During the trial, the jury heard how Letby told one mother, "trust me, I'm a nurse", as she killed one baby.

"I think this was about power," says Dr Carter Woodrow. "Saying, 'trust me, I'm a nurse', all the time knowing what she was going to go and do... it's like somebody with a card up their sleeve that they're almost laughing about."

Suspicions increase

Colleagues became suspicious of Letby within weeks of the first attack.

Dr Stephen Brearey, the head consultant on the neonatal unit, reviewed the deaths of Child A, C and D in June 2015. He found Letby was the only nurse on shift for each of the deaths.

In October 2015, consultants became increasingly concerned when they saw a spike in deaths that were "unexplained and unexpected" - a highly unusual occurrence in neonatal wards meaning there was no prior indication in the 24 hours before that death may occur.

Consultant Dr Ravi Jayaram alerted management but was told "not to make a fuss". He was even forced to apologise to Letby and attend mediation for accusing her of wrongdoing, news outlets reported.

Other colleagues who reported Letby were told there was no evidence against her.

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'A lot of suspicion'

Speculation grew as Letby would be on shift or near a child during every suspicious death.

Her reputation became so infamous that one staff member who worked at the hospital told Sky News: "There was a lot of suspicion when alarms would go off, during the night especially, there would be a phrase colleagues would use - 'I wonder if Lucy is working tonight'."

"That's exactly how it was, so people knew exactly what was going on," nursing assistant Lynsey Artell said.

Then and now, all evidence against Letby was circumstantial - there is no CCTV, no witnesses to her crimes.

But by July 2016, after several more warnings by senior consultants, Letby had been moved off the neonatal ward and put into an administrative role. An internal NHS investigation followed.

But the hospital only contacted police in early 2017, asking whether they thought an investigation was necessary - almost two years since the prosecution said Letby first attacked and well over a year after colleagues first became suspicious.

Letby caught

Letby was arrested more than three years after her killing spree started.

On that day in July 2018, she was relaxed and speaking in a calm, quiet tone after officers knocked on her door.

She let them in, wearing a blue hoodie with white and pink writing, as well as blue tracksuit bottoms. Her shoulder-length mousy blonde hair was hanging down around her face.

Ten minutes later, police bodycam footage recorded Letby being escorted out of the house in handcuffs and put into a police car where she told officers she just had knee surgery.

During a police interview that same day, she remained calm. When asked if she had been concerned about a rise in mortality rates at the hospital, she said: "I think we'd all just noticed as a team in general, the nursing staff, that this was a rise compared to previous years."

She was released after her first arrest but was rearrested in June 2019 when she was bailed pending further inquiries.

Letby was rearrested and charged in November 2020 three years after the investigation - named Operation Hummingbird - started.

Letby on trial

Letby on trial was a very different person to Letby the quiet nurse.

She was now 33 - eight years on from her first attack. She was smartly dressed, her hair now dark brown and longer than in pictures used by the media.

She was seated in the glass-fronted dock - her parents were seated in the gallery opposite her in courtroom seven at Manchester Crown Court.

Her mother frequently made eye contact with her daughter and mouthed "I love you" as the gruelling trial went on.

Spoke quietly and calmly

When Letby was called to give evidence in May, she spoke quietly and calmly and was asked repeatedly to raise her voice.

At times she was vigorous in her defence and firmly denied the charges. She pointed the finger at other colleagues and blamed general hospital failings.

But she repeatedly contradicted herself, muddled her story and became frustrated with the prosecution's questions - a far cry from the cool and collected nature she had displayed during her killing spree.

Letby cried when speaking about the impact of the arrest and trial on her, when photographs of her bedroom were shown and when speaking about her cats. But, as the prosecution pointed out, the tears stopped when the topic of the deaths arose.

Britain's worst child serial killer

She bowed her head and cried again when the first verdicts were delivered.

Susan Letby broke down sobbing as her daughter was led away from the dock, whispering "you can't be serious, this can't be right", into her husband's arms.

During the second set of verdicts, when she was found guilty of murdering four babies and attempting to murder two more. As the jury delivered the outcome of its deliberations she was emotionless, but her shoulders began to shake as she stood to be taken back down to the cells.

Letby refused to leave the cells and appear in court for the third set of verdicts when she was found guilty of three more murders and three more attempted murders.

This time, John and Susan Letby were silent, resigned, and leaned on each other with their eyes closed.

The verdicts were delivered after more than 100 hours of deliberations by the jury of seven women and four men.

For her sentencing on Monday, Letby made it clear she would refuse to appear in person or via video link.

Who is Lucy Letby?

Letby has never explained her transition from a very ordinary woman to Britain's most prolific child killer.

It is something her victims' families will have to fathom in the coming months and years as they grapple with a public inquiry and their harrowing grief.

Deputy senior investigating officer at Cheshire Police Nicola Evans said this "must be really hard for families to accept".

"I don't know whether we will ever be able to answer that question [of motive], and only Lucy Letby can answer that."