The jury in the Old Bailey trial of three teenagers for the murder of Pc Andrew Harper has been discharged due to the coronavirus pandemic.
Henry Long, 18, and two 17-year-old boys were accused of killing Pc Harper in August last year.
The 28-year-old Thames Valley officer became entangled in a tow rope as he tried to apprehend quad bike thieves, jurors were told.
The stricken officer was probably knocked unconscious as he fell, then dragged more than a mile along country lanes behind a Seat Toledo car driven by Long, the court was told.
Colleagues desperately tried to save him but he suffered catastrophic injuries and died at the scene near Sulhamstead, in Berkshire.
Long, of Mortimer, Reading, admitted manslaughter and conspiracy to steal a quad bike but denied murder.
The two youths, who cannot be named for legal reasons, admitted conspiracy to steal but denied murder and manslaughter.
Pc Harper’s widow Lissie and other family members attended the trial which opened on March 10.
Over two weeks, the jury viewed harrowing dash-cam footage and heard a string of eyewitness accounts, with one describing how he at first mistook Pc Harper’s body for a deer.
Last week, the jury dropped from 12 men and women to 10 due to jurors going into self-isolation.
On Monday, Mr Justice Edis made a statement in court that the remaining jurors were discharged and the trial adjourned.
He said he had made the decision with a “heavy heart” after a third juror went into isolation over the weekend.
He said: “It is with great regret that I have decided to discharge the jury and to adjourn this trial.
“I have taken this decision with a heavy heart because I am acutely conscious of the need of those who loved Police Constable Harper, who would have been 29 yesterday, for this process to come to a conclusion.”
The judge set a review hearing on June 1 to set a date for the trial to start again.
The defendants remain custody until the fresh trial on a date to be fixed.
The trial had been one of eight at the Old Bailey to continue last week despite the pandemic.
More than a dozen high-profile Old Bailey trials had already been postponed following measures to delay the spread of Covid-19.
Last Tuesday, it was announced that upcoming criminal trials lasting more than three days would be put off.
Earlier the same day, another Old Bailey jury convicted the Manchester Arena bomber’s brother Hashem Abedi of 22 counts of murder, attempted murder and conspiracy to cause explosions.
On Monday, further measures were announced putting criminal trials on hold.