Joel Donaldson, 21, allegedly punched a victim in the face before snatching her phone just steps from Brooklyn Borough Hall. He then tried to get away on foot, but didn’t get far. His droopy blue jeans — which left his boxer shorts exposed — kept slipping down as he ran. A cop who was directing traffic nearby spotted the bungling bad guy’s sorry sartorial situation and hurried after him. Donaldson made it only about a block before his pants were completely around his ankles, allowing the officer to tackle him. More