The lead Detective who caught Rhys Jones killer has left the force in a row over his rank.
Det Supt Dave Kelly was said to be furious after being told he would be stripped of his title which Merseyside Police said was on an acting basis.
He led the team of officers who worked to bring murderer Sean Mercer and his gang to justice.
Despite working under immense pressure in the national spotlight, Mr Kelly was called to meet Assistant Chief Constable Patricia Gallan last month.
During the meeting, he claims he was told he was to have his rank downgraded, sending him back to being a Detective Chief Inspector.
Having just completed his 30 years service, Mr Kelly was eligible to retire at any time.
The married father of 17 year old triplets planned to stay on, with the murders of Liverpool prostitute Anne-Marie Foy and shot Fazakerley dad-of-one Stephen Lloyd still unsolved.
But the perceived demotion, seen by some in the force as 'a slap in the face,' changed that and using up his remaining holiday, the Everton- born detective worked only a few days more after the meeting.
Rhys was shot and killed on August 22, 2007. The police team collected eight months of evidence against 18-year-old Croxteth Crew member Mercer and six others.
They were jailed for a total of nearly 40 years.
Mr Kelly was also in charge of the investigation into the murder of three- year-old Francesca Bimpson when he left the force.
He was also the first detective at the scene when toddler James Bulger was found dead.
A Merseyside police spokeswoman said: Dave Kelly has decided to retire from the Force whilst still in the role of temporary Detective Superintendent.
Dave Kelly decided to retire from the Force a couple of weeks ago, shortly before his temporary role was due to come to an end. As a result, he will retire on a substantive Superintendent's pension.
Mr Kelly is a highly respected detective, and we wish him well for the future.
The force added: Merseyside Police does not appoint an officer to a higher rank without them going through the necessary application, recruitment and selection process.
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