Vexinor
I don't know the real way it would be handled by a judge, they are often arbitrary. But for example I don't think a judge would be convinced by the fact that the data was not destroyed but specifically the keys when using the duress pin.
Are you allowed to take a suitcase that disappears the contents after an amount of time if you don't enter the lock password? It doesn't sound illegal to me but idk.
You would want to have backups if you had this feature, right? Because presumably you have data worth protecting that you want to keep. Although I would also highly respect simply sticking to your values if you didn't have anything incriminating.
So you have backups, why not wipe the phone and travel with it empty. Idc about a fresh phone looking suspicious, in most cases you wouldn't unlock it unless they're gonna use physical means anyway.
In my interpretation you would be on the strongest legal ground by refusing to speak because it's protected by the 5th and 1st amendment in the US.
The thing with all these solutions is that a government that coerces a password can put you in jail for anything already. It's not a fair playing field in many countries.
You are also protected when court forces you to chose
But that makes me think about countries with key disclosure laws that require a judge to sign. If the auto wipe didn't cause legal issues or caused less than that could make the feature useful.
If more people use duress password, law enforcement will be forced to either charge you with destruction of evidence when entering the destruction pin (if that's a lesser charge then it could be positive) or they will not enter the given password in order to not destroy evidence. This feature is seriously smart by GrapheneOS because its effectiveness would improve over time.
Knowledgeable people: Are there technical reasons this wipe timer can't be implemented?
IANAL!