So what is the move if you are caught with your pants down, and a LEO is requesting access to your actual phone? Does a factory restore wipe all data, or is in necessary to wipe, fill up with bunk data, wipe again?
I don't know about everyone else but my phone is has data including me talking about controversial opinions, intimate photos, and various other data that I would not want anyone else to have.
In the US, use passwords to protect your phone. Passwords have been held by courts to be testimony and thus protected by the 5th Amendment. Patterns, swipes, facial recognition and fingerprints have been held by courts to be the equivalent of "keys" and you can be required to turn them over upon being ordered by a lawful authority (such as a police officer demanding them). Passwords require a court order and if you have a competent attorney, they can argue that revealing the password would result in self-incrimination (and this can spend a lot of time in court before anything happens).
First, it would vary by phone -- but if LEO is requesting your phone and do not have a warrant (yet), they could still seize the phone citing exigent circumstances. The exigent circumstances being that if they left the phone in the custody of the subject, then they will likely delete the contents or at least could delete the contents. Once the phone is in LEO possession then they can take the time to apply for a warrant to search the device.
So -- if you get to the point of LEO requesting your phone and you have data on your phone, then it is too late.
In the US, unless we are talking about a border search, LEO will still need a warrant to search your phone. I'm unsure if this is what you meant by "pants down" tho :)
I don't know about everyone else but my phone is has data including me talking about controversial opinions, intimate photos, and various other data that I would not want anyone else to have.