Denial of qualified immunity for custodial arrest and interrogation over the course of two days on the basis of a warrant issued to produce the arrestee in court at a certain time for a hearing to determine if she should be detained as a material witness. Although the procedures violated a state statute, the variance from the terms on the face of the warrant created a Fourth Amendment violation. Sufficiently clear to be contrary to law despite lack of on-point precedent in the circuit.
Arrestee's return to the police station on the next day was not voluntary, given instruction to do so and reminder that police had an arrest warrant for her.
http://www.ca2.uscourts.gov/decisions/isysquery/c248c3bb-2a44-49a0-968d-6c71d649d45e/1/doc/17-1281_opn.pdf#xml=http://www.ca2.uscourts.gov/decisions/isysquery/c248c3bb-2a44-49a0-968d-6c71d649d45e/1/hilite/
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.