To answer your question, yes, it is standard procedure to keep a person handcuffed (even after he/she blows 0.00). DWI is not an alcohol exclusive charge. Drugs (legal or illegal) could have played a factor in this case. Doesn't sound like it, but let's admit it, we do not have all of the facts (from either side).
The trooper obviously felt that he had probable cause to arrest the female for DWI. Luckily, in NC we have magistrates that hear that probable cause before it's decided whether they agree with the facts.
It is my understanding in NC, after a person is arrested only a magistrate (or other judicial official) can release that person. This would explain why the trooper had to transport the female across to the county to the magistrate. It sounds as though the magistrate did not concur with the trooper's probable cause and thus released the female. In which case, the system worked.
Please reserve judgment (against both sides) until all the facts come to light and knowledge of laws and policies are understood. Based on the video from Wrightsville Beach PD it is obvious that some of the claims made by the female and her husband were inflated.
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