Earlier quoted context omitted.
No, I mean, disable Touch ID before any potential situation where the phone might be seized for any reason, not after a judge had ordered you to unlock the phone with a thumbprint.
The moment you believe the phone is going to be seized by law enforcement and you act accordingly to make it more difficult or impossible to retrieve data from it, you are guilty of spoliation / tampering of evidence. This is the same set of laws that makes it illegal to shred papers before law enforcement can get to them. Locking or erasing your phone is simply the digital equivalent.
I think you could just argue that you didn't want the disturbed and/or wanted to save some battery.