Mackenzie is a Sergeant in the United States Air Force stationed at Stargate Command. His post is as a technician in the Stargate Operations room, responsible for the activities there.
He was in the Stargate Operations room when the Stargate was stolen by The Trust. He along with MSgt. Walter Harriman were questioned by Dr. Daniel Jackson. (SG1: "Endgame")
He was in the Stargate Operations with CMSgt. Walter Harriman with Harriman telling him about the newest arrival, Lt. Colonel Cameron Mitchell who was in the Embarkation room staring at the Stargate. (SG1: "Avalon, Part 1")