Mad, but you wouldn't expect a flight crew to ask every passenger: "Do you per chance have an arrest warrant outstanding?"
Also, persons of interest don't necessarily have a warrant of arrest outstanding on them, but their flight from the country in question might be viewed in a dim light in the line of "don't leave town for a while" if they do end up getting on a plane to "get the hell out of Dodge" so to speak.
So as far as a flight crew is concerned, a judge/prosecutor would be hard-pushed to prove that they knew the person in question was told not to leave town, or had a warrant outstanding.
S.