Of course, prosecutors are concerned that opening themselves up to civil liability could have a "chilling effect," but quite frankly I want their behavior "chilled" if they're fabricating evidence or coercing witnesses to lie, which is what allegedly happened in this Iowa case. According to Raw Story:
The blogs Simple Justice and Crime and Federalism analyze competing amici briefs in the case, which are all available here. The CATO Institute also weighed in, and there's a discussion over at the Volokh Conspiracy over the Department of Justice's contention that prosecutors enjoy "absolute immunity." Jonathon Adler points out that police officers, by comparison, have only "qualified immunity," noting that "it seems incongruous to defend the position that prosecutors should have greater immunity for deliberate misconduct of this sort than do police officers." Doesn't it, though?
In 1978, Iowa teenagers Curtis McGhee Jr. and Terry Harrington were sentenced to life imprisonment after being convicted of murdering a security guard. After serving more than two decades, both men were released after Harrington obtained "previously undisclosed reports from the Council Bluffs Police Department that pointed to the existence of another suspect for the murder," according to court documents.The two men claim that in investigating the murder, Pottawattamie County prosecutors had coerced a witness to implicate them, "disregarded obviously false details" of the witness's accounts, "coached" the witness to give an account more consistent with the known facts of the case and then "coerced" other false witness testimony to corroborate that account.
County prosecutors, however, invoked "prosecutorial immunity," a concept University of Iowa College of Law Professor Todd Pettys described to Raw Story as "this notion that no matter what a prosecutor does at trial they can't be sued."