Former teacher Sion Jenkins is facing a third trial after a jury failed to decide whether he murdered his foster daughter eight years ago.
Sion Jenkins left the Old Bailey with his wife Christina Ferneyhough
Mrs Justice Rafferty discharged the Old Bailey jury after being told on Monday it was unable to reach a verdict.
Mr Jenkins, of Belgravia, London, denied battering 13-year-old Billie-Jo with a tent peg at the family home in Hastings, East Sussex, in 1997.
The 47-year-old will remain on bail as prosecutors seek a third trial.
Nicholas Hilliard, prosecuting, told the judge that the Crown wanted him to face trial again. A hearing will take place in the future to fix a date.
The jury heard evidence for more than two months before coming back on Monday after 27 hours and 43 minutes of deliberations.
The judge had given them a majority verdict instruction on Friday.
Billie-Jo was battered to death while painting patio doors
However, the jury foreman told the court there was no prospect of them being able to reach a verdict if they continued deliberating.
After discharging them, Mrs Justice Rafferty said: "You have done your civic duty in which no-one could have done better.
"I know it is unsatisfactory from your point of view that you have not reached verdicts, but what you should do is remind yourselves of the time, care and dedicated attention you have given this case."
The retrial began on 20 April with the prosecution saying Billie-Jo had been hit at least five times with an 18in metal tent peg.
The jury later heard that she suffered 20 separate injuries and would have died almost instantly.
Much of the evidence centred on blood spots found on Mr Jenkins' clothes.
The prosecution said he was sprayed with blood when he attacked Billie-Jo, but the defence argued that she breathed the blood droplets onto Mr Jenkins as he tended to her after the attack.
Jurors also visited the murder scene at the Jenkins family home on 5 May.
They examined the spot in front of the house's patio doors where Billie-Jo's body was found.
Mr Jenkins gave evidence over the course of four days at the retrial.
He denied lying in a 999 call and said he found an "horrendous" scene on discovering Billie-Jo's body.
Mr Jenkins was originally jailed for life in 1998 but has been on bail since his conviction was quashed and he was released by the Court of Appeal in July 2004.
He had been living in Aberystwyth, Wales, pending his retrial.