A man has been told he will spend at least 40 years in prison after murdering schoolgirl Toni-Ann Byfield and a man she regarded as her father.
Joel Smith shot the seven-year-old and drug dealer Bertram Byfield at a bedsit in Kensal Green, London, in 2003.
Toni-Ann, who was under the care of Birmingham Social Services, was hit in the back after she saw Mr Byfield, 41, shot by rival drug dealer Smith, 33.
Her mother Roselyn Richards condemned the "callous and cold-blooded killing".
Mr Justice Gross told Smith: "However grimly accustomed one becomes to violent crime there is a particular horror in the shooting in the back at close range of a seven-year-old girl - that is the hallmark of this case.
"Drugs and firearms combine to make an evil mixture."
In a statement read by her solicitor Andre Clovis, Ms Richards said Toni-Ann had "such a bright future".
"Her love for life could not be dampened until she crossed paths with Joel Smith," Mr Clovis said. "A man who could shoot a seven-year-old girl in the back does not deserve to rejoin society."
Ms Richards' statement added: "Having heard the evidence I believe Joel Smith did not act alone. I hope police inquiries will continue, to arrest, prosecute and convict others involved in this terrible crime."
The court had heard Smith, of no fixed address, believed he had committed the perfect crime, leaving no witnesses or clues.
He did not leave any DNA or forensic evidence and there was no CCTV in the area.
The prosecution said on the night of the murders, neighbours had heard four shots followed by silence.
Smith, who was known as Cocaine or Caine, fled London for Liverpool following the shootings in September 2003.
But he was tracked down two years later while serving a prison sentence in Liverpool after former friends and acquaintances, appalled by the death of the child, turned on him.
In court, Smith denied the murders, saying another man had admitted being the killer to him.
Bertram Byfield thought he was Toni-Ann's father, but post-mortem examinations later revealed he was not, the court heard.
The pair had been out shopping for a school uniform for Toni-Ann
The schoolgirl had been allowed to visit Mr Byfield despite his criminal past, which had seen him jailed for dealing in crack cocaine in 1997.
She was visiting Mr Byfield in his bedsit in an ex-offenders' hostel on the day the pair were killed. Birmingham Social Services was subsequently criticised for its care of Toni-Ann.
"We've made really significant changes to address all the recommendations of an independent review," Peter Hay, Birmingham City Council's strategic director of social care, said on Friday.
"At the end of the day however, I can't guarantee that armed gunmen won't walk into a room and shoot people. And at the end of the day, that's what lies at the heart of this case."
Smith was jailed for life for both murders, with a recommendation he serve a minimum of 40 years for the killing of Toni-Ann and 33 years for the murder of Mr Byfield.
Outside court, Det Supt Neil Basu, of the Metropolitan Police, said: "Toni-Ann was a complete innocent who was executed in cold blood - shot dead with a single bullet to the back and she cannot have known what for.
"No-one won here today. Toni-Ann will never be eight years old."