Community beat officer Ian Ivancic, allegedly pushed Niall Corbett against a police van before repeatedly punching him on the head.
He is further accused of abducting the teenager by bundling him into the back of the vehicle then driving off. Mr Corbett, who is now 17, gave evidence yesterday at Aberdeen Sheriff Court on the first day of the trial.
He claimed that he was at a house party in Balmedie's Chapelwell Drive that had become out of hand before he was allegedly assaulted.
The court heard he had refused to move from the street. Mr Corbett said: "He came over to me and grabbed me and I shrugged him off.
"I was thrown up against the van and that's when I got punched. I got punched by the police officer, two or three times. It was kind of like an uppercut."
Mr Corbett said he was then placed into the back of the van during the alleged incident on February 9, 2013.
Special constable Robert Ballantyne, 67, who was on duty with constable Ivancic at the time of the alleged incident, also gave evidence.
Mr Ballantyne, who was awarded the Queen's Police Medal in 2008, said that he had seen no evidence that Mr Corbett was assaulted.
He said the teenager was waving his arms at Ivancic as the police constable ushered youths up the street.
The trial continues today.