Was I there or was I not there?

[Mike Hussey]

Fitz upsets with Billy showed up at 344 Wash:

Fitz: But you weren't at f*cking home. So where the fu*k were you?
Billy: I was at the grocery store with no signal, all right? When I got the signal, I got the call. What the f*ck do you want from me? Was I there or was I not there?

What does it mean, "Was I there or was I not there" ?
"Was I there or was I not there?" Is trying to ask, in a disgruntled way, if Billy was at the store while at the same time asking Fitz in a sarcastic way if he was sure Billy was at the store?
Source: "The Departed" (a 2006 American crime film directed by Martin Scorsese and written by William Monahan)

 

[jutfrank]

He's making a very clear point that although he was late, he did turn up eventually—that he was there. He's telling Fitz to stop accusing him of not being there.

 

[GoesStation]

He's asking rhetorical questions to reinforce the point he wants to make.

 

[Tarheel]

Try:

Fitz is upset with Billy.