A traveler who prays behind someone he is unsure about: does he complete the prayer or shorten it?

Question : Yes, or behind someone he is unsure about.

Answer : I mean, if he prays behind someone he is unsure about—whether that person is a traveler or a resident. This only happens in places where there are many residents and travelers, such as an airport. An airport has residents and travelers; sometimes they are identified by a mark, and sometimes they are not. If they are identified by a mark, the matter is clear. For example, if we see a soldier in the airport, he is a resident. If we see a person carrying a travel bag, he is a traveler. If we are unsure and there is no evidence to support that he is a traveler or that he is a resident, then he is required to complete the prayer. Why?
They said that this is because one of the conditions for shortening the prayer is to intend it with a firm intention, not with hesitation. The person who prays behind someone he is unsure about does not know whether he is a traveler, in which case he would pray two units with him, or a resident, in which case he would pray four units with him.