I've seen a couple of arrests (being recorded) in which the cop said that once they placed you under arrest, then they can't "undo the arrest". These were in 2 different states and very recent.
I heard that many times in the early 1980's from other officers, but never from any college or training course I took.
The city prosecutor that I was referring to was very adamant about not placing any one in jail if the officer
came into evidence that indicated the suspect did not commit the crime. He wanted the arrest/processing to end.
If the suspect has already been booked into jail, it is far beyond the officers authority to do anything but
complete an accurate report and allow the prosecutor to handle it.
I also had a conversation with a county attorney, who became a district court judge,
I think he was also a college professor when he was younger.
I asked about the words "you're under arrest". He laughed and said there is nothing
"magical" about that phrase. He also said, do not follow through with the arrest if it is in error.
Again, do an accurate and truthful report. Now, the video recording makes for more truthful
police reports.
Of course, once a person is placed under arrest, they are required to comply with the arrest, nothing
has changed there. If a person resist an arrest for a crime that they are found not guilty of, they
can still be found guilty of resisting arrest. (hope that makes sense?)
I hold a college degree in LE, but it's from the 1980's. Someone else may have legal precedent on this rare area of
LE.