A person hasn't violated the law by uttering or possessing counterfeit money unless the person has reason to know the bill is counterfeit. If the store clerk didn't observe anything suspicious about the bill before completing the transaction and the Police officers couldn't visually detect that it was a counterfeit bill then there is no reason to believe anyone using the bill could have known it was counterfeit.
Minnesota Criminal Code, Chapter 609
609.632 COUNTERFEITING OF CURRENCY.
§Subd. 3.Uttering or possessing.
Whoever, with intent to defraud, utters or possesses with intent to utter any counterfeit United States postal money order, United States currency, Federal Reserve note, or other obligation or security of the United States, having reason to know that the money order, currency, note, or obligation or security is forged, counterfeited, falsely made, altered, or printed, is guilty of offering counterfeited currency and may be sentenced as provided in subdivision 4.
The Police would have to had seen Mr. Floyd actually passed the counterfeit bill before seizing his person at gun point, unless the $ 20 bill was such a reasonable person should have known it was fake but that is not what the facts suggest.
"A seizure of a person, within the meaning of the Fourth Amendment, occurs when the police's conduct would communicate to a reasonable person, taking into account the circumstances surrounding the encounter, that the person is not free to ignore the police presence and leave at his will. " SOURCE
At this point it doesn't appear they can even prove that Mr. Floyd ever departed his vehicle once it stopped across the street from the store. If he never went into the store then there obviously is probable cause to believe he passed a counterfeit bill in the store.
Minnesota Criminal Code, Chapter 609
609.632 COUNTERFEITING OF CURRENCY.
§Subd. 3.Uttering or possessing.
Whoever, with intent to defraud, utters or possesses with intent to utter any counterfeit United States postal money order, United States currency, Federal Reserve note, or other obligation or security of the United States, having reason to know that the money order, currency, note, or obligation or security is forged, counterfeited, falsely made, altered, or printed, is guilty of offering counterfeited currency and may be sentenced as provided in subdivision 4.
The Police would have to had seen Mr. Floyd actually passed the counterfeit bill before seizing his person at gun point, unless the $ 20 bill was such a reasonable person should have known it was fake but that is not what the facts suggest.
"A seizure of a person, within the meaning of the Fourth Amendment, occurs when the police's conduct would communicate to a reasonable person, taking into account the circumstances surrounding the encounter, that the person is not free to ignore the police presence and leave at his will. " SOURCE
At this point it doesn't appear they can even prove that Mr. Floyd ever departed his vehicle once it stopped across the street from the store. If he never went into the store then there obviously is probable cause to believe he passed a counterfeit bill in the store.