Please help settle silly debate (SPOILER)

I agree with you. I think not only did he do it deliberately, he relished in watching the "light bulb" come on for Marty. It was all a sick game for him.

he did it on purpose. he was telling Vail that he was weighing the options of letting him know or not letting him know and bask in his glory. He decided to mind phuque him, and played a trick on him to see if he would figure out what he said meant. And Vail did.

Swing away, Merrill....Merrill, swing away...

100% certain a slip. He might be a psychopath, but even psychopaths make mistakes, they're not infallible. I don't even understand how anyone could see this as anything but a slip? He had nothing left to lose, if he wanted to gloat to Richard he could've done so quite easily.

Yet he didn't, he kept pretending and pretending, and when Richard figured it out he just rolled with that instead, and decided to go down the gloating route. Because that is one thing Richard's character and Edward's character share; arrogance (although Richard is not a narcissist while Edward clearly is)

Did he slip on purpose to test Richard? Yeah, right, that's what he wants you to believe in retrospect. He got overconfident, I'm sure he was bursting with glee from the inside while he was talking to Richard in that cell, he couldn't help himself and made a mistake, luckily for him it was one he could afford to make.

FYI, narcissists have difficulty admitting when they're mistaken, at best they'd admit to mistakes that they have in the meantime already corrected (i.e. being caught by the cops).

Not a slip at all. He badly wanted Vail to know, but he wasn't going to just say it. He gave him a clue to see if Vail would figure it out.

Good question. A bit of both?

I think he slipped up without meaning to. Only when Vail goes back and quizzes him does he then decide he's going to admit the whole thing. You can see when Vail walks out of the shot to begin with, Roy is still playing the innocent Aaron character. Why would he still be like that when there's no reason to be with Vail seemingly walking away believing in his BS? Also he says during his admittance "I got caught though". Surely that refers to just then when Vail caught him out. I don't think it can refer to getting caught after the murder because presumably it was his plan to get caught, and if it wasn't then it's not in keeping with how smart he is for concocting the split personality charade.