United States v. Diaz-Fonseca, 1:12-cr-00242

Williamson was convicted of conspiracy to possess with intent to distribute methamphetamine and received a reduced sentence after the government filed a 5K1.1 motion; initial sentence 115 months, later reduced sua sponte to 92 months.
After beginning federal incarceration, Williamson testified in a Georgia state murder trial at the state's request; the defendant in that trial was acquitted.
Williamson's counsel asked federal prosecutors to file a Rule 35(b) motion for a post-sentencing reduction based on his state cooperation; the government declined.
The government cited distrust of Williamson stemming from his clandestine recordings of conversations with FBI Agent Tony DePrizio and Williamson's allegations of agent misconduct that were forwarded to the OIG.
Williamson moved to compel the government to file a Rule 35 motion, claiming the refusal was vindictive and constitutionally irrational; the government argued it has no duty to file and cited credibility concerns.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the court may review the government's refusal to file a Rule 35(b) motion	Williamson: refusal was vindictive and irrational, violating the Constitution	Government: no obligation to file; refusal based on lack of trust/credibility concerns	Court: Plaintiff failed to make the required substantial-threshold showing of an unconstitutional motive; review not permitted

United States v. McNeese, 547 F.3d 1307 (11th Cir. 2008) (government discretion to file substantial-assistance motion review limited unless defendant shows unconstitutional motive)
Wade v. United States, 504 U.S. 181 (1992) (Rule 35(b) confers a power, not a duty, on the government to move for sentence reduction)