If a judge issues a warrant allowing the police to compel the use of biometrics, can a person use the wrong finger? Courts can't compel someone enter their PIN. So can a court compel not only biometric "use" but the correct biometric?

My Android forces PIN entry after 5 wrong fingerprints.

If you refuse to tell them which finger you used, and comply by only pressing whichever finger they ask you to press, they will have a 10% chance of getting in each time.

So if you chose only 1 finger and you chose it randomly, they will have a 50% chance of getting in after 5 attempts.

And hope they're biased against the middle finger

You've always been able to do this on iOS as well, but it risks an obstruction of justice charge.