כי כאשר יקום איש על רעהו, "for like a man who rises up against his fellow,⁠" in Sanhedrin 74 our sages explained to us why the Torah describes the situation of the נערה המאורסה, the betrothed girl who became the victim of a rapist in the field, in such a cumbersome fashion, using such a parable comparing the situation to murder. We would have assumed that all the Torah had to say is that she cried out to no avail According to the Talmud, the Torah wanted to teach us that the two crimes, murder and rape, have features in common which enable us to apply the law applicable in one situation to the other situation in a reciprocal manner, i.e. the language of our sages: הרי זה בא ללמד ונמצא למד. The law of the murderer contains elements which are applicable to the law pertaining to rape, whereas the law of rape contains elements which we can apply to the law about murder.
Just as one must prefer to suffer death rather than commit the sin of murder based on the dictum of Rava: 'who said that your blood is redder than that of the person you are asked to kill in order to stay alive,⁠" so if someone threatens you with death unless you rape a woman you must rather suffer death than commit that crime. This law applies even if the woman to be raped is not married.
Our sages in Sanhedrin 75 tell of an incident when some man became love-sick over unrequited love. When his family turned to the doctors to ask how he could be cured, the doctor said that until he would have his craving indulged, i.e. sleep with the woman in question, he could not be cured. The Rabbis ruled it would be better that he die than that the woman submit to his sexual advances. In reply to the question whether at least he could have his libido assuaged by seeing the woman in question in the nude, the Rabbis were adamant, refusing that the woman in question expose herself to that man. In answer to the further question whether the woman could talk to that man from behind a fence, the rabbis did not even permit this either. (There is a dispute in the Talmud whether the lady in question was married or not.) Nonetheless, the reason given by the scholars who refused the girl in question to even speak to the infatuated man from behind a fence gave as their reason that it is not permissible to expose the girl's family to shame on account of someone who cannot control his libido. Even speaking to the individual from behind a fence is considered as equivalent to closeting herself with him.
Seeing that the Torah adds the comment that there was no one to act as the rapist's victim's savior, it appears that had there been such a person nearby he would have been obligated to save the girl from being raped even if the savior would have had to kill the rapist to be. The same holds true, of course, in the case of saving a potential murder victim from his assailant by killing him. When one observes a situation which will result in murder unless one stops the murderer by any means available one must use all such means including killing the potential murderer.

This is also the reason why when a woman who is in labor and is likely to die unless the baby about to be born is killed, must be saved at the expense of the life of the infant about to be born. The general rule is that it is permissible or obligatory to kill a רודף, someone clearly intending to kill an innocent person. The latter rule obtains only until the baby's head and the greater part of its body has left the mother's womb. Once this has happened halachah treats both mother and baby as separate lives and it is forbidden to save one at the expense of the other. We have confirmation of these rulings in Oholot 6,6 where the Mishnah teaches that in order to save the life of a mother in distress due to difficulty in giving birth one may remove organs of the fetus piece by piece from the womb seeing her life takes precedence over that of an unborn child. However, if the greater part of the baby had already emerged, one may not decide which life to save and has to leave this to natural forces.

The question is asked in the Talmud there: "why can we not save the life of the mother in the aforementioned situation seeing that we have a rule that if a minor is a potential murderer, in the act of perpetrating murder, that he may be stopped at the cost of his life? Why is this infant different from that situation? The answer given is that the infant in the process of being born is not viewed as someone bent on murder as it is his natural function to emerge from the womb for the sake of its own life. He is as if programmed by heaven to be in a life-threatening position vis-a-vis his mother.
The reason that the Torah in our verse describes the victim of the rape as צעקה, having cried out for help, (when in fact this is merely a presumption) is that she is viewed by the Torah as if she had cried out, i.e. the Torah gives her the benefit of the doubt (Ibn Ezra). Alternatively, the meaning of the words is "if she had cried out there would have been no one to help her.⁠" In other words, she is not charged as even if there is evidence that she had not called out this was due to the knowledge that it would have been useless.