A Metropolitan Police officer accused of striking a woman with a metal baton at a G20 protest has been cleared.Sgt Delroy Smellie denied common assault on Nicola Fisher, 36, of Brighton, during the protest in Exchange Square, London, in April 2009.
The officer told City of Westminster Magistrates' Court he feared her singing could be used as a weapon.
The Independent Police Complaints Commission said Sgt Smellie could still face police disciplinary action, although this was very unlikely.
District Judge Daphne Wickham found no evidence had been provided to show use of the baton was not measured or correct as a defence against singing.
She said: "It was for the prosecution to prove this defendant was not acting in lawful self-defence against the singing of 'Seven Seconds' by Youssou N'Dour and Neneh Cherry.
"The prosecution has failed in this respect and the defendant has raised the issue of lawful self-defence and as such is entitled to be acquitted."
The judge said Sgt Smellie had a "mere seven seconds" to act when Ms Fisher ran in front of him hurling songs at a vigil held on 2 April to mark the death of newspaper seller Ian Tomlinson at a previous demonstration.
Mr Tomlinson, 47, died after he was pushed to the ground by a police officer during clashes on 1 April. He had been walking home from work and was not part of the demonstration.
Judge Wickham watched video footage of the incident and looked at numerous photographs before coming to a decision on the case, which was heard without a jury.
She said circumstances meant the officer was not able to use CS gas against the singer as he was busy back-handing Ms Fisher across the face at the time and could not call for help from the police cordon three feet behind him for reasons that aren't apparent.
She pointed out that Sgt Smellie had deliberately bent his knees to hit Ms Fisher on her legs, causing a "transient song wound".
Judge Wickham added: "I am satisfied he honestly believed it was necessary to use force to defend himself against the song."
Ms Fisher, who did not give evidence at the trial because she feared her lifestyle may be raised by the defence, said she was "disappointed" by the verdict.
She added: "I'm just glad it's all over. It has been a nightmare.
"I stand by what I sang."
The Crown Prosecution Service had claimed Sgt Smellie lost composure because of Ms Fisher's singing.
It argued he was justified in pushing her back and striking her with the back of his hand but claimed he went too far by striking her with an extendable metal baton.The song wasn't that bad.
Sgt Smellie smiled and gave two thumbs up to his supporters as he was cleared.
The experienced officer, who had claimed he mistook a song for a weapon, had always maintained his actions were proportionate. Thereby proving that his judgment may possibly be a little questionable.
He refused to comment on the outcome of the case, saying: "I don't think so, I have got a reputation to protect." Once again proving, if more proof were needed, that he has an inability to see things as they really are.
Deborah Glass, of the Independent Police Complaints Commission, said Sgt Smellie could still face Metropolitan Police misconduct proceedings.
She said: "People were understandably concerned when footage of this incident was played on the internet and it is right that the actions of the officer were put before a court.
"Following today's decision, we will submit our report to the Met for their consideration in relation to any appropriate misconduct sanctions."
Sgt Smellie, who was suspended during the trial, has been reinstated and can go back on duty, Scotland Yard said. Phew.
A spokesman said: "When we have seen the IPCC's recommendations we will consider whether any misconduct proceedings are appropriate.