There are a lot of arresting scenarios in the US. Everyone is saying, yep, always cuffed. Well, that's really only for street cops who are in uniform, arresting you on the street or at your house etc. But in a case like Trump, let's say it's a white collar crime that's being investigated behind closed doors by Federal or State police. If it's a case that has to be built against you, and you have a lawyer, and are asked to come in voluntarily for questioning etc, then it's more like a series of meetings that are happening before an actual arrest. And at one meeting they may have the indictment ready to actually charge you, and say we are now going to arrest you for this crime, or through your lawyer, they say you have to surrender yourself and come in to be booked. You are cooperative and already in the building, they will just walk with you to booking, no cuffs. If you're on the street, a regular cop doesn't know if you have a weapon on you, he's alone, he will usually cuff you for safety. If you're in a building full of cops and you gave gone through a metal detector and have no weapons, they're is no need for cuffs. Additionally, in small towns, if it's a woman or an elderly person, I have seen cops just take them to the back of the cop car with no cuffs.