Legal Question in Criminal Law in Maryland

Yes they must always be sworn in. Theoretically it can be done from anywhere in the courtroom, but most judges will make them come up to the witness stand. But in some smaller courtrooms in rural counties the witness stand is either just at the State's Attorney's table or next to it, so it feels more informal. The idea is to impress upon the person the importance of the oath they are taking, which is why you must raise your right hand and swear to the oath (or affirmation for non-religious types).

If the parties know that a witness is going to take the 5th, then the summoning party may decide against calling the witness in the first place.