Shocking footage has emerged of the moment a police officer is seen forcefully throwing a teenage girl to the ground . Senior Constable Steven Trewin has been charged assaulting with Cassandra Swann , who was 19 at the time of the incident , the ABC reported . In the video , a blonde woman is seen hitting a police officer in the neck with her hand . Scroll down for video . Senior Constable Steven Trewin is accused of assaulting Cassandra Swann who was 19 at the time . The officer then grabs the woman by the arm and forces her to the ground in one rapid motion . Trewin told a court in Perth , Western Australia he was trying to stop the woman from hitting him . The incident was caught on CCTV inside the Northbridge police complex on August 25 , 2013 . Ms Swann and her friends had come to the station to report they had been attacked by some men while they were leaving a nightclub . A police officer is seen grabbing a blonde woman in CCTV footage on August 25 , 2013 at Northbridge police station in Perth . The police officer said Ms Swann was swearing it at him and he had to arrest her for her disorderly conduct . She was drunk at the time Trewin allegedly assaulted her and had been swearing at him . He then arrested Ms Swann when she did not leave and did not stop throwing profanities at him . Trewin told the court while he was taking her into custody she hit in the face twice with what he believed to be a blunt object . ' I then transferred to the arm bar [ arrest technique ] to force her down to the floor , ' he said . The woman is then forcefully thrown to the ground by the officer . The magistrate will make a decision about the case . 'My intention was to stop her striking me . I intended to force her to the ground , not to throw her to the ground . ' While he was questioned about his behaviour by the prosecution , Trewin said he thought he followed the proper procedure to arrest Ms Swann . The magistrate residing over the matter will make a decision about the case later this month . Sorry we are not currently accepting comments on this article .
Steven Trewin is accused of assaulting Cassandra Swann who was then 19 . She was at Northbridge police station in Perth when the incident happened . In the video , a police officer is seen taking a blonde woman by the arm . She is seen attempting to hit the police officer by his neck with her hand . He is then seen forcefully throwing her to the ground in one rapid motion . Trewin said he was stopping Ms Swann , who was drunk , from hitting him .