We start with the proposition that you cannot sue the prosecutor, who has absolute immunity from suit so long as the misconduct took place in pursuit of his official duties. Doesn't matter what he does, doesn't matter what he says. You can't sue him, and if you don't like it, lump it.
The case is Flagler v. Trainor, decided on November 21. Flagler was a domestic violence victim who was the chief witness at trial her ex-boyfriend. Trainor was the assistant district attorney who was prosecuting the abuser. Trainor swore to the local court that he thought Flagler was going to leave the area to avoid testifying against her abuser and that Flagler was not returning his phone calls or cooperating with the case. Following the material witness hearing, the County Court decided to take Flagler into custody and held her overnight without bail. Her cell phone was also confiscated. Flagler says that Trainor misled the County Court about Flagler's alleged refusal to testify and that Flagler had every intention to appear at trial. According to the lawsuit, Trainor's lies cost Flagler her liberty, at least temporarily.
Flagler cannot Trainor under the absolute immunity prohibition. Flagler tries to get around this by arguing that Trainor was actually acting as a complaining witness and not as an advocate. This argument has some basis in Supreme Court authority, but it does not work here. The Court of Appeals (Wesley, Calabresi and Lynch) says that "seeking a material witness order is within the prosecutor's 'function' as an advocate. A prosecutor employs prosecutorial discretion when determining whether to seek such an order."
But Flagler may be able to go after Trainor in other ways. Absolute immunity does not shield prosecutors from suit if they defame someone. Trainor told the press that Flagler was "hiding out" before the trial. The defamation claim is reinstated. So is Flagler's claim that Trainor unlawfully accessed her voice mail when Flagler's cell phone was seized. That's because absolute immunity does not shield prosecutors from investigatory acts.