He suffered permanent brain and spinal damage in the May 2009 incident, and can no longer talk, walk or feed himself. Harris' doctors say he'll need 24-hour care for the rest of his life.
But witnesses said things didn't have to end this way.
"I was floored, because it was like, 'Oh, my God, did those cops just kill that guy?'" said witness Micah Perry in court on Thursday.
Perry was among the first to testify at a civil trial in which the Harris family is suing King County for $25 million in damages.
Deputies chased Harris because he was mistakenly identified as a suspect in a stabbing. As the deputies went to arrest him, he ran. Harris' family members say the man didn't know those chasing him were deputies. Witness Ron Cody, who saw the incident from just a few feet away, said he didn't know at first, either.
"I said, 'Hey, who are you guys?' 'We're the police.' I said, 'Well, why did you do that? You didn't have to do that, because he was giving up,"' he said.
In the moments after the tackle, Cody said, he refused to leave the area.
"I wanted to bear witness to something I thought was unjust," he said.
Deputy Matthew Paul was not charged with a crime, but his actions are now being questioned in this civil trial.
Even though the deputy's actions are being questioned, he is not on trial. Paul remains a deputy with the King County Sheriff's Office.
The incident occurred in Seattle, but the trial was moved to Pierce County for trial as King County is the defendant in the suit.