When a traffic cop struck a woman across the face so hard that he broke her nose, he was acting in self-defence, a Düsseldorf court ruled on Tuesday.

The 55-year-old cop had stopped the woman as she was driving the wrong way down a one-way street back in October 2014.

The burly cop, who has been in uniform since 1977, told the court how he tried to issue the woman a €20 fine, but that she started screaming madly in protest.

Several witnesses state that at this point the policeman went to his 250-kilogram motorcycle and mounted it. The woman then approached him from behind and grabbed his shoulder.

The cop told the court that he was afraid that the woman was about to throw him from his bike.

“I was in a position from which I could be attacked – I was vulnerable,” he stated.

So he turned around and struck the woman in the face, claiming he couldn’t tell what the woman would have done next.

The woman, who had her three children in the car at the time, saw things differently.

She told the court that she had originally not wanted to pay the fine but had then changed her mind. The policeman had simply walked away, though.

“I couldn’t believe how I was dealt with,” she said.

She described the punch as “as K.O. strike to the face”, adding that all she had done was put her hand on his arm.

But the defence cited witnesses who recounted how the woman had acted like a little child and become hysterical.

It was regrettable that the woman’s nose had been broken, but the officer’s bike could have fallen over, the policeman's lawyers argued.

The judge agreed.

“You knew that you had acted improperly,” he said, reprimanded the woman for not owning up to her behaviour in court.

The officer, meanwhile, had acted in self-defence, he decided, explaining that it was irrelevant that the target of his punch was a petite woman and not a bodybuilder.

With the ruling, the judge cleared the officer of the charge of bodily harm and prohibited the woman from receiving compensation.