Rape is done by criminals. Even in India punishment for rape is death or life imprisonment. But we dont need "witnesses" for it. We have scientific ways of ascertaining if its rape or not. And obviously we dont put the woman to death if there are no witnesses unlike in Sharia law.
And having sex before marriage is also not wrong and 100 lashes is as good as death. The person will definitely die if you whip them 100 times. And that for having SEX?! Consensually?
I wont even go into adultery. There are people that are married whose relationship might be broken so they turn to others. But I dont think Sharia considers any of this. Thats why its outdated.