In United States v. Doe, 865 F.3d 1295 (10th Cir. 2017), the Tenth Circuit held that the government's refusal to file a substantial-assistance motion under 18 USC 3553(e)---where such a motion was contemplated in a plea agreement---may be subject to either a constitutional challenge or a contractual challenge (or both). Earlier this month, the Tenth Circuit clarified Doe, in United States v. E.F.
First, remember that if your sentencing goal is below both the guidelines range and the statutory mandatory minimum, you will need both USSG 5K1.1 and 18 U.S.C. 3553(e) motions from the government. The principles of Doe apply to both types of motions, and apply as well if the government files one type of motion but refuses to file the other (the Tenth Circuit only assumes this latter point for purposes of E.F.'s appeal, but suggests that such application "makes sense").
Second, a Doe contractual challenge proceeds in three steps: (1) the defendant must allege bad faith; (2) the government must rebut that allegation with facially plausible reasons; and then (3) the defendant must come forward with evidence to question the government's proffered reasons. As to step (2), it is facially plausible for the government to withhold a substantial-assistance departure motion if the client withholds information about ongoing criminal activity. "[F]ull
cooperation surely requires disclosing valuable information, particularly about
ongoing criminal activity." This is an important point to emphasize with any client who is interested in cooperating.
Third, if you are going to complain about the government not filing a motion, be prepared to meet Doe step (3). Defendant E.F. failed to satisfy this step, and therefore lost his challenge both in the district court and on appeal.