[csunbird]

For iphones, just tap the power button repeatedly, it will force a password entry to unlock.

[35fbe7d3d5b9]

If you have Siri enabled, you can also say "Hey Siri, whose phone is this?" – Siri will answer whose phone it is, but also will disable Touch/Face ID.

Do one of these things at the beginning of any custodial situation.

[jjeaff]

At least on Android, turning off or restarting your phone will work as well. Because you must enter your pin or password upon first starting up rather than use biometrics. At least, that seems to be the default. It may be a setting somewhere to turn that off.

[jaywalk]

5 presses, to be exact.