A £200,000 reward is being offered for information leading to the conviction of those responsible for murdering nine-year-old Olivia Pratt Korbel.
It is the biggest reward offer in Crimestoppers’ history.
It was previously £50,000 but was increased after a private donor offered £100,000 and the charity’s founder, Lord Ashcroft, matched it.
“This case has been incredibly shocking, not just for those who are directly affected, but also for Liverpool and the nation as a whole,” Lord Ashcroft said.
“I am delighted that with the support of a private donor, Crimestoppers can now offer a record £200,000 for information to catch Olivia’s killer.”
Olivia was killed in Dovecot, Liverpool on 22 August after a gunman fired shots into her home as he chased another man.
She was hit in the chest as she stood behind her mother, who was hit in the wrist.
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Nine arrests have been made so far, but they have all been released on bail and no one has been charged.
Police said today that officers had spent 15,000 hours on the case, that there were 2,000 exhibits, and that thousands of hours of CCTV had been looked at.
Detective Chief Superintendent Mark Kameen said the man who was chased and shot by the killer remained in hospital.
The weapon used to kill Olivia was revealed as a .38 revolver; and that a second gun in the case was a Glock self-loading 9mm pistol – used in three incidents on Merseyside in last few years.
People can contact Crimestoppers anonymously via its website or on 0800 555 111.