If your spouse gets killed, the detective knows the public story. Now he wants to know if the guy brought it on himself somehow. So a quick look around the house makes sense. Is it tidy and normal? Does it match the public "professional with happy family" story? Or was the guy also making meth in his garage? Maybe running a brothel? Head of a wacky cult? Got a bunch of illegals working as slave labor in restaurant kitchens? Stuff happens, but maybe he's dead for a different reason than just random bad luck.