Here are some of my initial design thoughts for our detective! The style I've gone for doesn't have to be what we're going for, it's just the easiest for me to visualise in.
Our Detective is a somewhat deluded chap. In head he wants to be brave, ruggard, strong and determined... in reality he is somewhat cowardly, depressed and overwhelmed by the world. He survives by bribing, dealing and turning a blind eye. The hunched shoulders and overweight physique offer up a sense of vulnerability, and the tipped hat and trench-coat lose all sense of coolness, becoming rather pitiful.
However, he envisions himself as a hero of damsels in distress and a persecutor of the wicked. He is stalwart, strong and uncorruptable, a paragon of honour and the law.