By this one particular we have been robbed of our presumption of innocence.
Logically, you can not presume someone is innocent while lying to them for the purpose of getting them to expose a crime.
It's like saying you offered someone a bribe because you presumed they wouldn't take it.
Excellent perception. They, by the mere fact of lying, are assuming a person is guilty. Hence, the ONLY means to confront such an attack, and it is an attack on our presumption of innocence, is to simply not cooperate and shut up. By far the best means of ending a confrontation with the police is to ask for a lawyer.