The incident took place last summer when the 39-year-old woman was shopping with her daughter in Solna near Stockholm.
The woman thought her daughter was kidding around when she asked her mother why the security guard was holding his mobile phone under the woman’s skirt.
“Very strange. I thought that he stood there to stop such things from happening in the first place,” said the woman to the newspaper Metro.
Upon being revealed by the woman’s daughter, the security guard attempted to flee the scene, but was chased down and eventually caught by the woman.
He admitted to the filming and was charged with sexual molestation.
But the Stockholm District Court acquitted the man, pointing to previous cases in which higher courts had overturned other sexual molestation convictions involving secret recordings because the victims did not know the filming was taking place until afterwards.
“In this case, she became aware of the molestation as it was happening. I’m considering an appeal,” said prosecutor Ewa Wintzell to Metro.