Instead of fumbling with your phone to turn on off biometrics just hold down the power button and reboot. Takes seconds and doesn’t look suspicious.
Next unlock will force a pin and skip biometrics. At least on android.
On my pixel phone, it’s a two step process, but you can press power and volume up. Then you choose Lockdown, and it requires a pin for the next time.
I just tried holding the power button down on my android and it doesn’t reboot the phone. I think they got rid of that feature and replaced it with opening up the useless Google Assistant crap.
You can change this in the settings to make the power button a power button again.
You need to turn them off, not on. The police can force you open your phone with them, but they can’t force you to use a code or pattern since that is proprietary.