The Internal Affairs Unit of the Durham Police Department released its findings Wednesday.
The investigation stemmed from a complaint from Stephanie Nickerson.
The 25-year-old Navy veteran had faced resisting arrest and assaulting an officer charges in the October 2012 incident in which she claimed an officer repeatedly punched her in the head and face -- leaving her with a broken nose, a black eye and swollen lips.
Nickerson told ABC11 in previous interviews that the incident began when police arrived at her friend's home early in the morning on Sunday Oct. 28 to investigate a report of a disturbance.
She said officers wanted to come in to search the property, but she told her friend that she didn't have to let officers in, and that's when things escalated.
"He was like put your arms behind your back, and I jerked my arm away and said no I haven't done anything wrong. And immediately after I jerked my arm back he threw me on the ground, he held me by my neck, and punched me repeatedly in my face and head," Nickerson said.
Some of the incident was captured on cell phone video. Although it is dark and blurry, friends of Nickerson were heard yelling for the officer to stop.
"He was hitting her with all his force. I could see him going all the way back, hitting her as hard as he could, and there was nothing I could do," eyewitness Tahveya Platt said.
The arresting officer, Brian Schnee, was not charged, but later resigned from the department.
The police department had been investigating for months, and said Wednesday that they found "Former Corporal B.D. Schnee used more force than was necessary against Ms. Nickerson while arresting her."
They also said they found insufficient evidence to prove Nickerson's allegation that she was arrested without cause.
The department said they take allegations of misconduct seriously and work to ensure that all complaints are thoroughly investigated.
Earlier this year, the Durham County District Attorney's office dropped all charges against Nickerson in connection with the incident. At that time, Nickerson and her attorney would not say what their next move legally would be.