If I thought there was any chance of police seizure at all, including interacting with the police, I turn my phone off.

My phone is encrypted, and can only be initially unlocked (decrypted) via the pin code.

Law enforcement has all kinds of methods to extract information from a powered on phone post-decryption. Once it's off and the storage onboard is encrypted, they either need to force me to give them the code, which, anything short of torture will not compel me to do, or brute force the pin, likely resulting in my phone locking out, requiring even more access, into my online accounts to unlock it (and/or wiping the phone), or brute force the encryption directly which will likely take millions of years with existing technology.

Even if a judge orders me to unlock it, I would refuse because the information on there, stuff I've said in confidence to others, could be used against me as testimony. The constitution protects me from incriminating myself. So I would simply argue (through my lawyer) that doing so would violate my right not to self incriminate.

Good luck coppers.