Just to clarify things here....
This requirement of having four witnesses only applies to adultery. If you want to accuse someone of adultery, then you need four witnesses to the act.
As you can see, some idiots have applied some really, really twisted logic and made it apply to rape as well. There is no such requirement which demands that the victim produces four witnesses. So long as there is sufficient evidence to prove that the woman has been raped by the suspect (DNA evidence, etc) then the charge sticks.
This article will help clear things up a bit:
http://www.irfi.org/articles/articles_351_400/rape_against_muslim_women.htmTo quote Sheikh Ahmad Kutty from the article:
A raped woman is a victim that must be treated with honor and kindness. She is not required to produce four witnesses to prove the crime done against her, nor is she punished for the crime done against her.
A woman who has been raped cannot be asked to produce witnesses; her claim shall be accepted unless there are tangible grounds to prove otherwise. To insist that she provide witnesses is akin to inflicting further pain on her. If anyone refutes her claim of innocence, the onus is on him to provide evidence, and she may simply deny the claim by making a solemn oath, thus clearing herself in public.
The Prophet (peace and blessings be upon him) said, “The onus to provide evidence falls on the one who makes a claim, and the one who denies (the same) can absolve himself or herself by making a solemn oath to the contrary.”