Why does Dubai (and other countries) imprison women who report being raped?

Question

Most of us have heard the grotesque stories about rape victims in Dubai (and probably other countries as well), who have been imprisoned for pre-marital sex after reporting being raped to the local authorities.

A woman can be imprisoned for admitting to pre-marital sex, because proving that a rape happened is next to impossible in Dubai, where four male Muslim witnesses are required. If a woman admits to being raped, and the rape cannot be proven by the legal system, the man or men walks free.

But why is there no burden of proof for imprisoning the woman? If sex has happened, by Dubai law, one of the parties is guilty of breaking the law. But not being able to prove that the accused is guilty doesn't mean that the accuser is guilty, by any standard of the law, as I know it. Does innocent until proven guilty not exist here?

Surely it is not illegal to be raped, and that is the only thing these women are admitting to? On what grounds are they imprisoned?

UPDATE:

As a comparison, I'd like to explore the following. A victim of consuming illegal drugs against their will, reports the crime at a police station/ hospital in the USA. Health workers perform a drug test, and find evidence of illegal substances. An investigation is started, but due to lack of evidence, no one is charged or convicted of drugging this victim. Could this now result in a criminal case charge against the one reporting being drugged, because the drugs are illegal to consume, and no evidence is found that this was done against their will?

Answer 1

Women are imprisoned on the grounds that they have confessed to engaging in pre-marital sex.

If you're looking for the reason why this is the case even when they've been raped, it's because Islamic law, specifically, Sharia law, states that this is the punishment for engaging in pre-marital sex.

Answer 2

The "logic" it appears is that the law says "having pre-marital sex is illegal" and "Having any sex with someone AND it was against his/her will is illegal". Thus, if an unwed woman is accusing a man of "Having Sex with someone and it was against her will" the crime of "Having sex out of marriage" is confessed too as she is unmarried and sex happened. The crime she is accusing is that the man did not have her consent to do it... and if the crime is not proven, she still had to testify that "Pre-marital sex happened" and at this point, in absent of a sucessful rape allegation, she's confessing to a crime.

Western law has a concept of this called "Affirmative Defense" which is essentially conceding one point of the accusation as fact in order to argue that the other point not fact. For example, in the U.S. the crime of Murder generally holds that two things must happen (and if neither one does, it's not murder): 1.) You killed someone (homicide) AND 2.) there was no justification for killing that person.

A classic affirmative defense to Murder is "Self-Defense" and requires that you acknowledge that the first element (You killed someone) is true BUT the the prosecution is wrong about the second element (The reason you killed the person was he was going to kill you and you had no other choice).

The difference between Islamic Law and Common Law (U.S.) is that an Affirmative Defense does not need to prove "beyond reasonable doubt" that it was self-defense and not murder, just that it's enough to not rule it out as a plausible explanation. In Islamic Law, the burden of proof is still required.

Please note that in the first sentence, I used quotes around "logic" as I believe one of the initial predicate conditions is false, thus the conclusion is not logical, but this part gets into a sort of mathematical logic that requires a lot of explanation I think would detract from the summery. Essentially, It's your math teacher saying "I understand why you got the answer you did because you showed your work, but your answer is still wrong."

EDIT: In response to the Update. Involuntary Intoxication is a defense though it is rarely used, as well as diminished mental capacity. With that said, if the person intoxicated against their will does nothing but report the crime, it's likely they will get an easier time than if they drunk drive after drinking spiked punch. If they are able to prove it, they would be legally not responsible for any crime committed while under the influence.