The jury in the trial of three teenagers accused of the murder of Pc Andrew Harper was discharged on Monday due to the coronavirus pandemic.
Henry Long, 18, and two 17-year-old teenage boys were charged with murder after PC Harper's death in Berkshire in August last year.
Last week, the jury dropped from 12 men and women to 10 due to jurors going into self-isolation.
On Monday, Mr Justice Edis said he adjourned the trial with a "heavy heart" after a third juror went into isolation over the weekend.
"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," he said.
He set a review hearing on June 1 to set a date for the trial to start again.
The court heard the 28-year-old Thames Valley officer became entangled in a tow rope as he tried to apprehend quad bike thieves in Berkshire in August last year.
Jurors were told the officer was probably knocked unconscious as he fell, then was dragged more than a mile along country lanes behind a Seat Toledo car driven by Henry Long, 18.
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.
The defendants remain in custody until the fresh trial on a date to be fixed.
More than a dozen high-profile Old Bailey trials had already been postponed following social distancing measures introduced 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.
The PC Harper trial had been one of eight slated to continue last week.
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.