[Mad Dawg]

It seems to me that this post and the general argument lumps together police, deputies, prosecutors, and judges. Once I arrest somebody, from then on it's out of my hands. The Commonwealth attorney may decide I was a dope or not. And if he decides to prosecute, the judge and jury have a role to play.

But if after I arrest somebody new evidence comes to light and the commonwealth attorney suppresses it, I might not even know that happened.

You use the word "they". Maybe a few nouns would clarify things. WHO told her what would happen if she changed her story?

[WindOracle]

The investigating officers. The ones she made her complaint to to begin with.