I'm afraid I haven't quite gotten over Marcus's phrasing for exposing two of the alibis. "Unless the minister was killed in a kinky sex game..." While it does seem quite likely that Zeller and Davies were not involved at all, I can't help but enjoy coming up with scenarios in which such a thing could have gone fatally wrong.
I'm sure someone will have something to say about this, but personally, I like to find a way to keep things light and entertaining. Comtemplating fatal foreplay certainly means no disrespect for the dead, nor the former suspects, especially not when it seems so unlikely it was how he was killed.