A Denver police officer accused of assaulting a 16-year-old boy in his custody was found not guilty Thursday afternoon.Officer Charles Porter, a 12-year veteran of the Denver Police Department, was accused of jumping and stomping on 16-year-old Juan "Willie" Vasquez, who was running away from officers.Vasquez, who suffered broken ribs, an injured kidney and a lacerated liver, claimed Porter used excessive force. Vasquez's brother said the officers jumped on Vasquez with both feet and beat him with a flashlight.The incident occurred near West 37th Avenue and Pecos Street in April 2008, as Porter was working as a officer in the Denver gang unit. Porter and two other officers -- Officer Luis Rivera and Officer Cameron Moerman -- were at the scene.Rivera and Moerman testified during the trial that they saw Porter jump repeatedly on the teen's back with both of his feet. However, neither officer reported the incident to supervisors. Porter's defense attorney claimed that Rivera and Moerman were involved in the beating but were covering it up.It took the jury two hours of deliberation to find Porter not guilty of first-degree assault.