Can only imagine what must have been going through Kristoph's mind at the moment he watched his apprentice produce a piece of evidence that decidedly should not have existed and present it in court.
Phoenix really made Kristoph watch Apollo present forged evidence in court and that's so fucked up and poetic of him.
Apollo's exact line on presenting that ace is "My reason is... uh... This!" Which implies that he's very unsure of what he's about to do or where it will lead. But Kristoph knows, and Phoenix knows too. Which is why the very act of Apollo presenting that ace was Phoenix's subtle message to Kristoph - "I know what you did seven years ago, and you're going to watch your own student make the same mistake and nail your coffin shut with it at the same time." And poor, poor Apollo is none the wiser that he is simply the conduit of this message.
Phoenix was a theater kid, and he can be quite cruel when he wants to be.
