No Remedy
Prosecutors have absolute immunity for courtroom advocacy and qualified immunity for investigative work. The absolute kind traces to a 1976 Supreme Court decision, not to the text of Section 1983, which Congress passed in 1871. The Court acknowledged it could leave a genuinely wronged defendant with no civil remedy. Federal prosecutors face a wider gap: no express federal cause of action exists.
Sources: Imbler v. Pachtman, 424 U.S. 409 (1976) · 42 U.S.C. § 1983