He knows

"Don't panic I knew you weren't a girl."

"You did, how?"

"Your voice's a little deep and you didn't try to change it. You look good for your first time out as a girl, have you been dressing up long?"

"No, just a little lingerie at first, then make up, and finally as you see me now."

"So did you set out to get some cock today?"

"What, no I just thought I would go out dressed up and see if I could fool anyone. I'm surprised you didn't get mad though I thought for sure you were going to beat me up."

"I've spent a bit of time in jail, there's plenty of white boys who are willing to give up their mouth and ass for protection, a few cigarettes, even ****, so you're not the first white boy I've fucked in the mouth and ass and you won't be the last either."

You suddenly realize what he just said, he hasn't fucked your ass yet, but he knew you weren't a girl and he brought you to his place any way, you were **** to suck his cock and only did it to prove to him you weren't a cop.