For if someone steals the phone?

As a speech.

"it would be funny if the border police typed it in to my phone"

I think you should read the other reply about not saying anything at all.

Not saying anything at all is one of the worst things you can do when questioned by law enforcement in the US (though "it would be funny" is a close second). The right way to remain silent is to loudly proclaim "I am exercising my right to remain silent."

> what other possible explanation is there for someone putting a PIN visible on their phone that wipes it while crossing a border?

Two obvious answers:

1. It's for the general case of lost/stolen phone.

2. It's for the owner. I can't remember numbers I don't type in, might as well keep it visible on the device.

There’s no way to prove intent if you keep your mouth shut and don’t answer anything.

Yea, that’s not how it works in practice. If they catch you standing over a dead body holding the murder weapon. Then you can’t just say they can’t prove intent if you keep your mouth shut.

Yea but that's where "reasonable suspicion" comes in a court of law. If you are standing next to a dead body, with a bloody knife in your hand.

And doing anything non-standard with your phone is going to shift the reasonable suspicion away from favoring you unless you can explain yourself.

That’s good advice to not talk, but it won’t necessarily save you.

They might be able to convict on that, but that sets a dangerous precedent imo, which is that doing anything preemptively to prevent searches is conviction worthy, including the preparation the OP suggested.

if the cops do that, they're breaking the law with that search already

theyll have a hard time showing that you intended for the government to break the law. first the government would have to admit breaking the law

Unfortunately I think they have pretty wide latitude to perform searches at border crossings.

claim your password to be some derivative of the duress PIN, for example: 1234 is password reminder for 2444 (one 2 three 4), the device is erased anyway.

>what other possible explanation is there for someone putting a PIN visible on their phone that wipes it while crossing a border?

For thieves, obviously.