Do we know specifically how Richmond's wife died? Yes, we know she was killed by a drunk driver, but is it possible she was knocked off a bridge into water, and she drowned? That would explain Orpheus' fascination with wanting to know what it was like when you drowned. I think it's someone working for him who had access to a campaign car, either Jamie or Drexler (maybe both?). Drexler makes sense because he's beaten hookers in the past, and the whole "apartment" scene with the girls swimming through the overhead pool was necessary for something. Jamie could easily have been involved in the cover up, to protect Richmond's campaign. Whether that was Drexler killing hookers or Richmond soliciting hookers, I don't know. My guess is that Richmond doesn't know about the murder but was, in fact, Orpheus.