I would say yes he deserves to be prosecuted, as a crime was committed regardless of whether he was caught for it at the time (A tree falling in a forest makes sound regardless of whether someone is there to hear it). As to the last question, I would say no she cannot, I strongly feel that consent is evaluated at the time the event occurred, and subsequent events cannot change whether consent was given or able to be given.
I would actually argue that depending on what she does with those pictures she also could be prosecuted (if she mails them to him that is distribution of child porn, even if they are pictures of her).
Think of this scenario. A woman is raped during a robbery by a masked man. She reports the rape, and they take DNA swabs but can't get a match, and don't find the man. Years later, she meets a man at a party, falls in love, and gets married. Then lets say her sister comes down with leukemia, and needs a bone marrow transplant. Both she and her husband get tested to see if they are a match, and then BOOM his DNA pops up as a match for the DNA collected in the rape kit (I know those systems probably aren't linked yet, but they should be, and this is a hypothetical). Her husband was the masked man (WHO saw that coming??? I should be a fucking screenwriter). Should she be able to grant him immunity for the past rape? Or should he be prosecuted no matter what because they know that a rape was committed and they have his DNA tying him to the case? Remember, the girl may not perjure herself, she cannot say that she had lied and that she had consented at the time (because that's not what happened), she can only say that NOW she retroactively consents. I would argue that the state and validity of the consent at the time of the act is all that matters.
