
In summary of all the fatawa that have been quoted, I'll list a few major points, inshaa'Allah:
1. The Islamic hudood (prescribed) punishments are intended to protect society from the spread of immorality. Hence, although the punishments are extremely severe, an equally high burden of proof is required to establish that the offence was publically witnessed. Consequently, Islam has set 4 witnesses who saw the act of penetration as the required evidence for the hadd punishment to be carried out for unlawful sex. This punishments are, as the IslamToday.com committee writes, The punishments for fornication and adultery are designed more to protect society from the open practice of licentious sexual behavior than they are designed to punish people.
Since the hudood punishments are intended to protect society from the spread of immorality, they punish those offences that were committed publically, where many could witness. In this manner, the punishments serve as a means of denunciation and condemnation by society of the sin. This is why prescribed punishments have been attached to those offences that are committed publically, in order that there be a strong deterrent from spreading immorality in society.
2. This does not mean that if an offence is committed which does not meet the standard of evidence for a hadd (prescribed) punishment, that it will go unpunished. No, on the contrary, the Islamic legal system has ta'azir (discretionary) punishments as well as the prescribed punishments. These discretionary punishments form a major aspect of the penal code in an Islamic state as they are usually the more common punishments.
3. With regard to rape, if it meets the standard of proof (i.e. four witnesses) for the hadd punishment, then the rapist will recieve that. If there are not four witnesses, it does not mean that the rapist goes unpunished. So long as there is sufficient evidence to establishg the guilt of the rapist, he can be punished severely according to a ta'zir (discretionary) punishment.
4. The nature of the punishment can vary according to the nature of the rape (all though all punishments will be very severe). Depending on the use of weapons and the extent of the force used, a more severe punishment may be given, often the same as that given in the case of hiraabah (armed robbery) (Qur'an 5:33). Victims of sexual assault are encouraged to report their cases to authorities so that justice may be served.

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