Stephen Yaxley-Lennon will be sentenced on Thursday for contempt of court over a video he broadcast from Leeds on social media which featured defendants in a criminal trial.
The former English Defence League (EDL) founder, better known as Tommy Robinson, was found to have committed contempt of court following a two-day hearing at the Old Bailey on Friday.
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Dame Victoria Sharp and Mr Justice Warby found Robinson was in contempt in three respects when he filmed men accused of the sexual exploitation of young girls and live-streamed the footage on Facebook, in breach of a reporting ban, outside Leeds Crown Court in May 2018.
Giving reasons for the decision on Tuesday, Dame Victoria said Robinson encouraged "vigilante action" in the video, which lasted an hour-and-a-half and was viewed online 250,000 times on the morning of the broadcast.
The judge said the words he used in the video would have been understood by viewers as "an incitement" to harass the defendants and "gave rise to a real risk the course of justice would be seriously impeded".
Throughout the Old Bailey hearing, Robinson denied any wrongdoing, saying he did not believe he was breaching reporting restrictions and only referred to information that was already in the public domain.
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But Dame Victoria and Mr Justice Warby found he was in contempt by breaching the reporting restriction imposed on the trial, by live-streaming the video from outside the public entrance to the court and by "aggressively confronting and filming" some of the defendants.
A number of Robinson's supporters who gathered outside the court on Thursday and Friday reacted angrily after the result was announced.
Robinson, 36, from Luton, Bedfordshire, broadcast the footage while the jury in the second of a series of linked grooming trials was considering its verdict.
The video was eventually viewed 3.4 million times after being shared following his arrest.
A reporting restriction was in place which postponed the publication of any details of the case until the end of all the trials involving 29 people, in a bid to ensure all defendants received a fair trial.
Robinson was jailed for 13 months after being found in contempt of court on the day of the broadcast.
He served two months in jail before being freed after the original finding of contempt was overturned by the Court of Appeal in August 2018.
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But the case was then referred back to the Attorney General, who announced in March that it was in the public interest to bring fresh proceedings against Robinson.
Dame Victoria and Mr Justice Warby gave permission for the Attorney General to bring a new case against Robinson at a hearing in May.
Anyone found in contempt of court can be jailed for up to two years, receive an unlimited fine, or both.
In an appearance on the far-right conspiracy theory website InfoWars on Monday, Robinson asked US President Donald Trump to grant him asylum in America, claiming he faced being killed in prison if he was jailed on Thursday.