Status and Authority of Off-Duty Officers

Jeff Welty blogged last week about State v. Capps, __ N.C. App. __, 2019 WL 2180435 (May 21, 2019). The central issue in that case was the state's use of a misdemeanor statement of charges, but there was a minor detail in the facts that caught my eye because it raises an issue I've been asked about more than once. What is the status and authority of a law enforcement officer when he or she is off-duty? What Happened? As Jeff summarized in his post, the defendant in Capps got into an altercation with the passenger in his vehicle while putting air in his tires at a truck stop. The argument escalated to the point that the defendant cut off the end of the hose, dragged the passenger out of the car, and attempted to assault her with the hose end. An off-duty deputy happened to be at the truck stop refueling his vehicle. When the deputy saw what was happening, he approached the defendant, "displayed his badge, and lifted his shirt to reveal his service weapon."  Undeterred, the defendant got back into his vehicle, drove around the store "burning" his tires, and then headed out through an intersection (between two other vehicles), ran a red light, and took off down the highway at a high rate of speed. If the facts had played out differently and the deputy had succeeded in detaining the defendant in Capps, would it have been a lawful arrest? Was the defendant resisting, delaying, or obstructing [...]