Here is a link to a BBC article about a study that was done of young adults who were asked to determine whether or not a certain “staged” event would be a rape in the real world. It’s interesting how many Shades of Gray there are . . .
(FYI – I’m personally of the opinion that, no matter what the technicalities of law require, if a person does not give advance informed consent that is both voluntary and sober, if anything sexual happens it should be classified as rape.)