Factual error: The 20 banknote shown is multicoloured, but the real one is plain blue. (00:40:40)
Factual error: Her name is wrong. In Russia if your father's last name is Chenkov but you are female, then your last name would be Chenkova.
Factual error: An airbag deploys in the police car when Salt crashes it through the railing and onto the road below. But this airbag should have deployed much earlier on when the car had experienced multiple head-on collisions with various other cars.
Answer: They have to at least investigate that kind of an accusation, and when Salt so vigorously resists arrest it basically confirms, in their minds, that she is in fact a spy.
Phixius ★
I actually kind of find it shocking that they would be willing to believe a guy who would do or say anything to save himself and since Salt was with the agency a long time, they could have at least given her the benefit of the doubt.