A teenage mugger took the witness stand yesterday and laid out for a jury the rules of the street that dictated why an actress and playwright on the verge of making it in New York was shot dead, while other mugging victims that night were allowed to live. It wasn’t the color of her skin, or the amount of money in her purse, the mugger said, but the victim’s attitude — her insouciance, defiance and disdain that made the mugger’s accomplice shoot the actress, 28-year-old Nicole duFresne, once in the chest, killing her. “What are you going to do, you...