False arrest? The would come under Title 42 US Code 1983 - Civil Rights; and probably some state related claims.
The DA and Crystal would be liable. Normally a DA would not be liable because a da who is not stupid does not get involved in the investigative aspect of a case. If, as I suspect, Nifong acted in the role of an investigator, he loses his qualified immunity, so he would be liable. On top of that, he refused to talk to the defense attorneys or look at the evidence of their innocence. That could easily be construed as deliberate indifference and would be a separate basis for personal liability.
Duke university might also have some liability in this area if they did suspend the two players prior to a conviction since they have a property interest in their schooling.
As for the city of Durham, that presents a very interesting question. If the Durham police department conducted a sham investigation and refused to talk to the defendants or look at their evidence of innocence; and pushed for an indictment (which doesn't seem to be the case) they would be liable under Monell v. the City of New York (USSC case).
The best way for the city to avoid liability, if the police did not recommend and especially if the police told the DA not to seek and indictment, would be to refuse to pay the legal bills of the DA when he eventually gets sued. Since it can never be the duty of a public official to violate the law, the DA would then have a hard time arguing he was acting in his official capacity.
Defamation
Lots of potential here. The DA is at the top of the list. He has all but said to the public and the media that these two guys are rapists. Stating that he is positive that a rape occurred and then later naming the defendants opens him up. He should have simply told the public he was investigating an allegation of rape, and when an arrest was made, should have simply stated that two suspects were arrested
Since speaking to the media is not a prosecutorial function, he has no immunity.
The Duke professors (so I have read) that stated in their classes, or outside of class, that the two players are rapists have major problems, maybe even more-so than the DA.
The talking heads in the media who have been alleging that these two guys are rapists could also have some significant liability, especially since many of them are not providing a "fair and balanced presentation of the facts". This would be a negligent reporting of the story which is all that is needed to prevail against them since the two players are 'private persons' under the law. The fact that the story is gaining widespread coverage does not make them 'public persons' for the purpose of defamation. In fact, it could easily be argued that members of the media have been malicious in their reporting of this story, which would make them liable even if the two players were 'public persons' for purposes of defamation.
There are also claims for malicious prosecution, and some other less interesting causes of action.
Thank you for so clearly explaining this. And laying it out.