Nine-year-old Olivia was shot by Thomas Cashman, 35, as he chased drug dealer Joseph Nee into her home in Dovecot, Liverpool, on 22 August last year.
The shooting came the day after gunman James Witham, 41, forced his way into Ms Dale's home in Old Swan, Liverpool, and killed her.
During his trial at Manchester Crown Court in March, Cashman's lawyers introduced evidence of other potential suspects in the murder.
Those named included Sean Zeisz, 28, and Niall Barry, 26 - who went on to be convicted of Miss Dale's murder - and Ian Fitzgibbon, 28, who stood trial for her murder and was cleared of all charges.
During Cashman's trial, the defence asked for information relating to Fitzgibbon, who was extradited from Spain in August to stand trial for Ms Dale's shooting.
The judge said Fitzgibbon was "believed to have left the United Kingdom around the time of this shooting having made arrangements to do so the day before".
He said: "As will emerge later in this ruling, the name of this man appears in intelligence as being potentially connected to this shooting.
"The defence is seeking disclosure of antecedent information about whether he did in fact leave the country and about what steps have been taken to find him."
The defence also wanted to obtain evidence about a feud involving the family of Joseph Nee.
Zeisz and Barry were jointly charged with conspiracy to commit grievous bodily harm to his brother, Jamie Nee, but both were acquitted at a trial earlier this year.
Joseph Nee was attacked and in an interview with police, he speculated that it was because people believed he was responsible for Barry's arrest.
Barry and Fitzgibbon did not match the height and build of the gunman who killed Olivia and were ruled out.
Telephone and ANPR evidence relating to Zeisz excluded him, the court heard.
During the course of the investigation into Olivia's murder, the court heard many names were mentioned as being responsible for it, including Cashman's on multiple occasions.
The defence application to introduce evidence about other suspects was dismissed by Mrs Justice Yip.
She said: "The issue in this case is whether Mr Cashman was the gunman."
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