What is the current state of the law on immunity for a prosecutor in a criminal case?

It is true that many of the earlier cases have seemed to say that the prosecutor's immunity is virtually absolute and that he may speak with impunity about an indicted defendant. Doubtless it is true that all too many prosecutors have acted on that assumption in times past. But at least by 1966 it had come to be recognized that improper pre-trial publicity endanger a fair trial and may constitute a denial of due process. In Sheppard v. Maxwell, 384 U.S. 333, 86 S.Ct. 1507, 16 L.Ed.2d 60 (1966), decided in June of that year, Mr. Justice Clark noted in reversing a murder conviction that,