"We still do not know what drove him to commit this appalling crime against a stranger." Does it have to be "driven" or do murderers murder & rapists rape so long as they think they can get away with it?
Phrasing this carefully, I should think the number of rape prosecutions and their final outcomes might support the perspective that it is something for which there's a high expectation of non-report, non-progression or legal exculpation.
Similarly, the increased use of the 'consent' defence even until the point of death, does seem to be associated with a change of charges to assault, misadventure or much lesser offences than murder or manslaughter (there used to be a rueful pronunciation of that as 'man's laughter' because it was so common for men to be charged with that rather than murder in the death of a woman).