One of the GrapheneOS people (I think) suggested keeping a bit of paper in your wallet with the duress pin, perhaps thinly disguised. Then the cops could try it on their own initiative. I suppose they'd become aware of that trick eventually, but then they wouldn't be able to use all those other genuine pins they find.
Today we see someone being arrested because they used a software feature. Next year we'll see someone being arrested because they played a cutesy trick and got the LEO to enter in the self destruct code.
The engineers and techies involved have so far shown themselves to have poor intuition for understanding how the law is going to react. I think it behooves anyone still listening to their advice to also check in with someone who has a good intuition for how the law will react to this new idea.
It's harder for them to argue you were actively destroying evidence; you could say that you had written the wipe pin there for a legitimate use case like both your wallet and your phone get stolen
A far better approach is for the US citizen to simply say "I chose not to provide my PIN".
The officer will say something like "That's your choice, but I will need to seize the device to conduct an analysis. It will be returned once the analysis is complete".
Then you shrug, and they will let you enter the US. The cops will try to get into the phone, fail, and return it to you.
Just bring a phone you don't mind losing for a few months.
This person was under "investigation" for protesting against cop city. The authorities were waiting for him to turn up at a place where the law would give them more power.
They were never going to let him just walk in. Eventually, they'd have to, possibly after lawyers and news would get involved, but it's not like saying "no" was going to end the ordeal right away.
