Investigators pieced together evil killer nurse Lucy Letby's murders with an unusual method - leading to "chilling" results.
The 33-year-old nurse was this week convicted of murdering seven premature babies and attempting to murder six more while working at The Countess of Chester Hospital.
Detective Superintendent Paul Hughes put a single detective on each individual case giving them "unique ownership" of every baby and kept all the evidence separate.
It meant each officer would not be influenced by what colleagues unearthed as things progressed. It comes as police are now investigating whether Letby - Britain's worst serial baby murderer - committed her first horror crimes at Liverpool Women's Hospital prior to her killing spree at the Countess of Chester.
Detectives will examine her whole career, with her convictions so far only focusing in on a period between March 2015 and July 2016 when 17 babies died and 15 suffered non-fatal collapses at the latter hospital's neonatal unit.
Man in 30s dies after being stabbed in park sparking police probeReferring to the original probe, Mr Hughes said: "We looked at it individually, every case needed to be investigated on its own merit. I wanted to allow people to come to a determination of what they were finding on their own." After six months using this tactic, Mr Hughes then introduced weekly team meetings, where investigators shared information. "All of a sudden the picture would start falling into place," he said. "It was chilling really at times, to see it drop into effect.
"A detective would give the update of their investigation, they would say, 'What happened in my case was…according to the medical evidence the collapse took place at this time, at this time the designated nurse went on a break handing over care to Lucy Letby, the parents left and the child collapsed,' then another detective would go, 'Oh my God, that's exactly what happened in my case.' Patterns emerged. That's what happened as we approached mid-2018," he added.
Should there be a statutory inquiry into the Lucy Letby case? Vote in our poll HERE to have your say.
Families of Letby's victims yesterday slammed a proposed Department of Health inquiry into how hospital bosses failed to notice her sick crimes despite multiple warnings. Legal reps labelled the action toothless because it won't have the power to allow people to come forward and give evidence.
A statement said: "This is not good enough. The failings here are very serious and an inquiry needs to have a statutory basis to have real teeth." It also claims the Countess of Chester is seemingly putting its own reputation above the safety of children. Other parents have been coming forward with concerns that the killer nurse also harming their infants, including one mum who said her son died at the hospital in March 2014, a year before the period relating to Letby's convictions.
Police are now reviewing the care of 4,000 babies Letby may have come into contact with during a spell at the Countess of Chester from January 2012 to the end of June 2016 and two work placements at Liverpool Women's Hospital in 2012 and 2015. Detective Mr Hughes said: "This does not mean we are investigating all 4,000. It just means that we are committed to a thorough review of every admission from a medical perspective to ensure that nothing is missed throughout the entirety of her employment as a nurse."