Doe starts to get aroused

As you continue to probe Doe's tight asshole with your fingers, you hear her moan lightly, then cover her mouth with her hand. A smirk on your face, you begin moving your fingers a little more deeper into her, causing her knees to give just a little.

"Look... look how nervous this is making me," Doe says, trying to divert attention from what her body is doing. "I'm shaking in fear."

"Yes," you observe appreciatively. "I don't think I've seen a prisoner look so... scared in their life."

"And since I obviously have nothing up my ass, we can put an end to this," she continues, a little more sternly.

You've already spent too long with your fingers in her ass for this to be considered in the same ballpark as a regular search. It's definitely time to change gloves and go for her pussy, and maybe see what trouble you can cause for her by playing with that. On the other hand, just because you didn't find anything in her ass didn't mean you didn't want to put something there. She was well-lubricated there now. You're sure she wouldn't let you mount her ass all that willingly, but neither would her efforts to stop you be all that effective.