After watching millions of TV-shows and movies I always thought that detectives and higher ranking officers of the U.S. police force don't usually wear uniforms during their normal work (apart from special official events), in contrast to normal officers patroling the streets. Therefore I always wondered why Deputy Chief Noland always keeps wearing his uniform during the whole runtime of The District.
Is it ever explained why he does this? Is there a special rule for the police of Washington D.C., or does he do this out of his own impulse, maybe to show a special commitment to his job or pride in it (yet what would this say about Chief Mannion not doing so)? Is there any further meaning to this? Or maybe it isn't as uncommon as I think it to be and there isn't much more to it.