Deuteronomy 22 (assuming you have read the whole chapter and are familiar with the context) is four scenarios of sexual impropriety, involving both false accusations and true ones. A judge is to take the evidence into consideration as he renders a verdict and punishment. The whole idea is protect the women from sexual abuse and life-ruining accusations.
Verses 13-19 are a false accusation. A new husband accuses his bride of premarital promiscuity. If she is innocent, damages are due. If she's guilty, she is to be punished.
Vv. 20-21 are a true accusation—a case of consensual sex with a married woman. If both are guilty, both are punished.
Vv. 22-24 are about consensual sex with an engaged virgin. If both are guilty, both are punished.
Vv. 25-29 are about the seduction or rape of an engaged virgin. If the man is guilty of rape, he is executed. If he is innocent, damages are due.
So, your question is about v. 28. There's a lot of dispute about the translation of the word (
patah: It means "to persuade; tempt; allure."). It is often argued to mean sexual intercourse without specifying whether it is consensual or not, and in fact, is translated this way elsewhere in the Old Testament. So maybe this isn't even about rape to begin with.
Sandra Richter, in her journal article "Rape in Israel's Word...and Ours," writes,
"The writer goes to lengths to distinguish this final law from the case of rape previously discussed (vv. 25-27). The girl in this verse could have been manipulated or be under what we would consider a proper age, but not assaulted. Therefore, this law is designed not to punish the man for a violent capital crime, but to protect the young woman from the economic and legal insecurities that this irresponsible man has introduced. She becomes a wife in perpetuity—an apt consequence for our 'walk-away Joe.' The seducer must offer a handsome mohar for a girl who may now no longer be able to attract a spouse."