[BeHoldAPaleHorse]

Now, if you saw a person cross the border, in the middle of the desert, how do you know he's committed a crime?

My understanding from a long time ago as a cop is that entry to or exit from the United States must be done through a legal point of embarkation/debarkation.

[Marine Inspector]

That's the basics.

If the person can't cross at a legal point of embarkation/debarkation, he can cross anywhere and has a specific amount of time (if I recall, it's 48 hours) to present himself for inspection.

Also, being a former police officer, what elements are needed to commit a crime?