The detective superintendent who spent three years hunting the killer of seven-year-old Toni-Ann Byfield told the Liverpool Echo it "cracked the case" through its coverage and appeals for information.
As a result of his efforts, Echo reporter Luke Traynor scooped an exclusive interview with Neil Basu, the detective who led the murder inquiry.
Joel Smith was last week jailed for life at the Old Bailey for gunning down Toni and the man she had believed was her father, drug dealer Bertram Byfield.
A huge manhunt had been under way to find the murderer, who killed Toni after she witnessed the murder of Byfield in a North London flat.
As soon as the Echo discovered the news that Smith, by this time the prime suspect, was hiding in Liverpool, it launched an appeal for information targeted at the city's underworld.
An officer was quoted saying: "Forget about petty gang rivalries — this is a little girl. It is absolutely horrendous. You may not want to inform the police, but for the sake of this dead child getting justice, you ought to."
The appeal sparked an influx of calls from Merseyside, including information from three inmates at Walton Prison, where Smith was by then serving time for crimes including GBH and affray.
Their evidence led to the arrest for the double murder.
Speaking exclusively to the Echo just minutes after the verdict, Basu said: "You broke the case. I have absolutely no doubt the appeals run in Merseyside were the difference to catching Joel Smith. After the appeals in the Echo, prisoners from Liverpool came forward to us by approaching a prison officer. The information they provided was invaluable."
News editor Alison Gow said: "The appeal attracted a lot of national press coverage, and the Liverpool Echo got mentioned a lot in the trial as it was a key part of the evidence of the prisoners who came forward and spoke out.
"Anyone who has an affinity with the Echo would feel really proud of what their local paper has achieved."
The Echo dedicated its front page to the conviction, as well as a double-page spread on Saturday.
Ã¢– The Willesden & Brent Times produced a four-page pull-out detailing the history of the Toni-Ann Byfield case from when she was murdered in September 2003.
It included a statement from Toni's mother, profiles of Bertram, Toni and their killer Joel Smith, along with a story detailing exactly how Smith was caught.
There was information about the continuing investigation — as police believe Smith did not work alone — and an interview with the head of Operation Trident.
The newspaper says it is the first time the publication has produced such a comprehensive report on a local murder.
Reporter Lorraine King said: "We felt we needed to answer all the questions readers would be asking about her death."
The Times printed 1,000 extra copies of the paper as it always sells out when featuring Toni's murder.