No, they have 5 tries, and most people use at least 2 fingers (I use 3) so you can unlock it with both hands. Furthermore, most people use at least their thumb

No, they have 5 tries, and most people use at least 2 fingers (I use 3) so you can unlock it with both hands. Furthermore, most people use at least their thumb. So if the judge said use your left and right thumb, the chance of succeeding would be a lot higher (statistically speaking). If you use, let's say, your pinky finger, the chance of a judge guessing the right fingerprint is even lower because he will try out the most obvious choices before that.