What is the current state of the law on prosecutorial vindictiveness?

"Actual vindictiveness must play no part in a prosecutorial or sentencing decision and, since the fear of such vindictiveness may unconstitutionally deter a defendant's exercise of his rights, the appearance of vindictiveness must also be avoided." United States v. King, 126 F.3d 394, 397 (2d Cir.1997) (internal quotation marks and brackets omitted). Accordingly, an indictment will be dismissed if there is a finding of "actual" vindictiveness, or if there is a presumption of vindictiveness that has not been rebutted by objective evidence justifying the prosecutor's action. See id. (internal quotation marks omitted). "A district court's factual findings on prosecutorial vindictiveness are reviewed for clear error and the legal principles which guide the district court are reviewed de novo." United States v. Johnson, 91 F.3d 695, 698 (5th Cir.1996).