For my story, I have a few ideas of where to go with it, but wasn't sure which, but I like this idea, but not sure if it legally work, plot wise. Basically the MC is a cop who wants revenge on the villain, or at least wants justice for what he did, should justice somehow be able to prevail in the end. The villain does not want the MC to kill him and knows that he is after him, so the villain plans to go to the police and turn himself in, in order to avoid being killed out of revenge. But this is where the plot hole comes in, because if the villain were to turn himself in and confess, even offering evidence, the confession and evidence, could not be admissible in court, since he did it under being threatened by a cop. Evidence does not legally count if it was the person gives it up, out of coercion. So is there a way in which he can turn himself in, and it would actually work, and he would go to jail? Or is the law pretty air tight on this one, and there are no exceptions that be used? I tried looking it up but couldn't find any, but what do you think, for the sake of the story?