. . . to help the government, but then the government refused to help them.
The Tenth Circuit has officially endorsed two approaches when the government refuses to move for a substantial-assistance departure despite your client's best (and risky) efforts. In United States v. John Doe, the Court clarified that your client may have both constitutional and contractual remedies.
First, as the Supreme Court held in Wade v. United States, "federal district courts have authority to review a prosecutor’s refusal to file a substantial-assistance motion and to grant a remedy if . . . the refusal was based on an unconstitutional motive" or "not rationally related to any legitimate government end."
And second, because parties to a contract have a duty to deal in good faith, the district court may review the government's decision not to file the motion for good faith. This review should take a 3-step Batson-like form:
"[A] defendant must first allege that the government acted in bad faith. The government may then rebut that allegation by providing its reasons for refusing to file the motion. Assuming those reasons are at least facially plausible, we hold that a defendant is only entitled to good-faith review if he or she produces evidence giving reason to question the justification the government advanced."