A British nurse, who penned a note stating "I am evil", was found guilty on Friday of murdering seven newborn babies and trying to kill another six in the neonatal unit of a hospital in northwest England where she worked.
33-year-old Lucy Letby was convicted of killing five baby boys and two baby girls at the Countess of Chester hospital and attacking other newborns, often while she was working night shifts, in 2015 and 2016.
The jury had been told she poisoned some of her infant victims by injecting them with insulin and others were injected with air or force fed milk, sometimes involving multiple attacks before they died.
The verdict, following a 10-month trial at Manchester Crown Court, makes Letby one of Britain's most prolific serial child killers. She was found not guilty of two attempted murders while the jury were unable to agree on six other suspected attacks.
Why did the nurse kill her innocent victims?
"I killed them on purpose because I’m not good enough to care for them," said a handwritten note found by police officers searching her home after she was arrested. "I am a horrible evil person," she wrote. "I AM EVIL I DID THIS".
Some of those she attacked were twins - in one case she murdered both siblings. She tried to kill one baby girl three times before finally succeeding on the fourth attempt.
"Lucy Letby was entrusted to protect some of the most vulnerable babies. Little did those working alongside her know that there was a murderer in their midst," said Pascale Jones, a Senior Crown Prosecutor from the Crown Prosecution Service.
"She did her utmost to conceal her crimes, by varying the ways in which she repeatedly harmed babies in her care."
"Lucy Letby was entrusted to protect some of the most vulnerable babies. Little did those working alongside her know that there was a murderer in their midst," said Pascale Jones, a senior prosecutor from the Crown Prosecution Service.
"She did her utmost to conceal her crimes, by varying the ways in which she repeatedly harmed babies in her care."
Letby will be sentenced on Monday and faces a very long prison term, and possibly a rare full life sentence.
Her actions came to light when senior doctors became concerned at the number of unexplained deaths and collapses at the neonatal unit, where premature or sick babies are treated, over 18 months from January 2015.
With doctors unable to find a medical reason, police were called in. After a lengthy investigation Letby, who had been involved in the care of the babies, was pinpointed as the "constant malevolent presence when things took a turn for the worse," said prosecutor Nick Johnson.
Pictures of Letby on social media portrayed a happy and smiling woman with a busy social life, and in one photo she was seen cradling a baby. But, during months of often distressing evidence, her trial heard she was a determined killer.
The jury was told how Letby had tried on four occasions to murder one baby girl before she finally succeeded, while when another of the victim's mothers walked in on her attacking her twin babies, she said to her: "Trust me, I'm a nurse."
At her home after her arrest, detectives found paperwork and medical notes with references to the children involved in the case. She had also carried out social media searches for the parents and families of the murdered babies.
Letby wept when she gave evidence over 14 days, saying she had never tried to hurt the babies and had only ever wanted to care for them, saying there had been unsafe staffing levels on the ward and its dirty conditions might have been a factor in the deaths.
"I have never murdered a child or harmed any of them," she said. She claimed four doctors had conspired to pin the blame on her for the unit's failings.
Letby told the jury she had written the "I am evil" message because she had felt overwhelmed and she had felt she was somehow incompetent or had done something wrong.
Prosecution describes Letby as a cruel liar
The prosecution said she was a cold, cruel, calculating liar who had repeatedly changed her account of events and her notes should be treated as a confession.
Detectives said they had found nothing unusual about Letby's life and could not determine any motive for why she had become a killer.
"The only person that can answer that ... is Lucy Letby herself," said Detective Superintendent Paul Hughes who led the investigation. "Unfortunately, I don't think we'll ever know unless she just chooses to tell us."
Police are carrying out further investigations into all the time Letby had worked as a nurse at the hospital and at another one in Liverpool where she had trained, to identify if there were any more victims.
"There is a number of cases that are active investigations that parents have been informed of," Hughes said.