Most statistics are based on police reports, not convictions. For crimes other than murder, there is a good agreement between police reports and surveys of victims.
Conviction data has a bias introduced by the the court, but it has a much worse bias from restricting to cases where a suspect is identified and apprehended.
Here are the New York Times, CNN, and NBC. Here is Wikipedia for background.
The case has made several appearances on LessWrong; examples include: