I was just reading a personal account of rape where it was claimed that most of her circle of friends had experienced rape at the hands of police, so possibly that's a good place to start.

Also, here's a couple of year old article that takes head on the question of how police deal with rape accusations. I can't recommend it enough, it won a Pulizter:

https://www.propublica.org/article/false-rape-accusations-an...