My idea was that the verb "to confess" implied that the object and subject was one and the same person. For example, to confess one's own guilt, sin, or "confess against oneself", but when I caught myself writing "You must confess against him." and was lost for any good synonym that wouldn't result in a much longer sentence, I started wondering whether this is acceptable English or not. I did find one such use of it in a printed book (regarding the Prisoner's Dilemma): "If you confess against the other and he remains silent then you can go free [...]" and my search returned a few articles that used confess similarly as a synonym for revealing one's knowledge about the sins/guilt of some other person than oneself. So, yeah, my question really just is whether it's a proper use of "confess", and if not, what's the word that does exactly what I want? For some odd reason the word "testify" rings completely false in the context.