A case pending at the U.S. Supreme Court was recently settled out of court, and the case withdrawn from consideration. It appears that there has been a settlement of $12M, for prosecutorial misconduct.
"This means prosecutors who step outside their traditional role and who act as investigators (in criminal cases) can still be subject to civil rights lawsuits just as police would be."
Prosecutors are normally immune from lawsuits involving work during trials. The 8th U.S. Circuit Court of Appeals decided in McGhee vs. Pottawattamie County in 2008 that plaintiffs could sue prosecutors under civil rights statutes if the alleged wrongdoing arose from investigatory work before the trial started.