Border patrol agents are trained to cause a person some discomfort or some confusion by asking the right question and watching for slight emotional reactions.
These reactions can be displayed by facial or speech signs and many others.
A good example is my father. He was born in Norway and came to the USA at the age of 13.
He grew up in Chicago and was in the US navy for some time, then moved to Portland Oregon.
He was about 70 yrs. old when my brother talked him into taking a trip into Mexico.
On the return to the US he was asked where he was born. For some reason my dad said Portland Oregon instead of Norway.
The agent quickly said get out of the car and come into the office. When they got into the office the agent said only," Why Did You Lie To Me" and nothing else.
My dad had sense enough not to argue. He said because if I said Norway we would be in this office for a long time.
He showed the agent his military service/medical cards and was released. He asked the agent how he knew and he said he could see and feel your fear.
My dad would never even consider another trip to Mexico or any where else out of the country.
Outoftheorg