A sex offences trial collapsed at Liverpool Crown Court today after a CPS paralegal tested positive for coronavirus.
One courtroom and the Crown Prosecution Service office at the Queen Elizabeth II Law Courts are now out of operation.
They will undergo deep cleans while court officials seek to track and trace any people who may have become infected.
The member of staff from CPS Mersey Cheshire was in work at the combined court centre in Derby Square yesterday.
He had direct contact with documents being used in court 5-2 - currently allocated for trials - on the building's fifth floor.
But he then received a positive result for a coronavirus test, which the ECHO understands he had previously taken.
As a result, the jury in the trial of a man accused of a series of sexual assaults against a young girl in Southport was today discharged.
Anthony Bloor, 30, of Brentwood Close, Eccleston, who denies any wrongdoing, will now face a retrial.
All personnel in court 5-2 - including the judge, counsel, clerk and 12 jurors - were advised to self-isolate and or seek testing, as a precautionary measure, and the CPS today said it had taken "immediate action" in line with Government guidelines.
After an emergency meeting led by the Recorder of Liverpool, Judge Andrew Menary, QC, it was decided the remaining crown and magistrates' courtrooms would remain open, with all other cases progressing as normal.
Detailed investigations are now ongoing to track and trace all of the CPS paralegal's movements and contacts, and the people he may have had dealings with.
Court officials believe they have identified all people and areas where there was a risk and have not been advised that it is necessary to take further measures.
The ECHO understands the steps taken by the court, including the discharge of the jury, were out of an abundance of caution, rather than Public Health England guidance.
However, the overriding aim of court staff throughout this pandemic has been to ensure that all court users, including the jury, are kept safe.
The risk of contamination from indirect contact, for example touching a piece of paper that an infected person has previously touched, is said to be so small as to be negligible.
Nonetheless, NHS track and trace guidance is being followed, so that anyone who has had close contact with the infected person has been told to self-isolate and or seek testing.
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Aksha Shahid, Deputy Chief Crown Prosecutor for CPS Mersey Cheshire, said: "A member of our staff who was working at Liverpool Crown Court has been diagnosed with coronavirus.
"The member of staff reported this to us and we have taken immediate action, in line with Government guidelines, to protect anyone else who may have come into contact with this person in the court building.
"HM Courts and Tribunal Service have closed the CPS room in the building and the court room where the person had been working. The jury has also been discharged. Both rooms are undergoing a deep clean.
"We will be monitoring the situation closely."
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Manchester Crown Court in Crown Square is currently closed after six staff there tested positive for coronavirus.
HM Courts and Tribunals Service took the decision to close and deep clean the court this week.
All visitors to Liverpool Crown Court are asked to observe social distancing and wear face masks in all public areas of the building, including landings, and no more than one person is allowed to use the building's lifts at any one time.
The building currently has four courtrooms allocated for socially distanced trials, a figure that is soon expected to increase to eight, making the centre the busiest court for trials in the country, along with London's Old Bailey.
From Monday next week, Liverpool Crown Court will also be testing a single 'Covid Court' - operating outside of ordinary court hours - as part of a month-long pilot scheme.
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Dealing with the simplest cases involving the least number of witnesses, single defendants and the shortest time estimates, it will operate in morning and afternoon sessions.
One trial in the morning will run from 9am to 1pm, with no scope for it to run into the afternoon.
The courtroom will then be cleaned over lunchtime, before a separate judge, court staff, barristers and jury will begin a new trial, sitting from 2pm until 6pm.