A sentence is final, with two narrow exceptions
A federal sentence is meant to stick. Congress said so directly: apart from narrow exceptions, a court may not modify a term of imprisonment once it has been imposed. One of those exceptions is the authority Congress preserved in 18 U.S.C. 3582, which provides that "the court may modify an imposed term of imprisonment to the extent otherwise expressly permitted by statute or by Rule 35 of the Federal Rules of Criminal Procedure." Rule 35 is therefore not a second sentencing or a general appeal. It is a limited tool with two separate uses, and each use has its own deadline and its own gatekeeper. If you are facing Federal Sentencing, understanding which door applies to you is the starting point, because the two doors lead to very different arguments.
Rule 35(a): fixing a clear error within 14 days
The first use of Rule 35 is correction. The rule states: "Within 14 days after sentencing, the court may correct a sentence that resulted from arithmetical, technical, or other clear error." That sentence carries three points worth slowing down for.
First, the errors it covers are obvious ones. An arithmetical error is a math mistake in the guideline calculation. A technical error is a slip in how the judgment was written or entered. Other clear error means a mistake that is plain on the record, not a close call the judge might decide differently on reflection. A sentence the judge intended, even one the defense considers too harsh, is not a clear error. Rule 35(a) fixes mistakes. It does not revisit judgment.
Second, the clock is short and it runs from a specific moment. Rule 35 defines its own starting line: as used in this rule, "sentencing" means "the oral announcement of the sentence." The 14 days run from the day the judge speaks the sentence in court, not from the later entry of the written judgment. In practice this means counsel must compare the oral sentence, the guideline calculation, and the written judgment immediately, while the window is still open.
Third, either side can flag the problem. The rule says the court may correct the sentence, and in practice the judge, the prosecutor, or defense counsel can raise an obvious error within the window. How it is argued is straightforward: point to the exact place in the record where the numbers or the words went wrong, show what the correct figure or language should have been, and ask for a corrected judgment. There is no balancing of sentencing purposes here and no new evidence. The question is only whether an obvious mistake occurred and what the correction should be.
Rule 35(b): reduction for substantial assistance
The second use of Rule 35 is the one most families ask about: a lower sentence in exchange for help against someone else. The controlling principle is that the defendant does not decide this. The government does. The rule states: "Upon the government's motion made within one year of sentencing, the court may reduce a sentence if the defendant, after sentencing, provided substantial assistance in investigating or prosecuting another person."
Every phrase in that sentence does work. The motion must come from the government. A judge cannot grant a Rule 35(b) reduction without it, no matter how real the assistance was. The assistance must have come after sentencing, which is what separates this rule from its pre-sentence sibling, USSG 5K1.1. And the help must be substantial assistance in investigating or prosecuting another person, meaning testimony, information, or cooperation directed at someone else's crime, not an account of the defendant's own conduct.
Timing creates two tracks. A motion made within one year of sentencing follows the general rule quoted above. A motion made more than one year after sentencing must fit one of three narrow categories set out in the rule: information the defendant did not know until a year or more after sentencing, information the defendant gave the government within one year of sentencing that only became useful to the government later, or information whose usefulness could not reasonably have been anticipated until more than a year after sentencing and which the defendant promptly provided once its usefulness became reasonably apparent. Late cooperation is therefore not automatically disqualified, but it must be explained inside one of those three boxes, and the government must still be willing to file.
Two further provisions shape how these motions are argued. The rule then adds: "In evaluating whether the defendant has provided substantial assistance, the court may consider the defendant's presentence assistance." Cooperation that began before sentencing, through meetings with agents, grand jury testimony, or trial testimony, can therefore support the motion alongside help given after judgment. And the rule provides: "When acting under Rule 35(b), the court may reduce the sentence to a level below the minimum sentence established by statute." For a person serving a mandatory minimum, that sentence is the reason Rule 35(b) matters most. Congress reinforced the point in 18 U.S.C. 3553(e): "Upon motion of the Government, the court shall have the authority to impose a sentence below a level established by statute as a minimum sentence so as to reflect a defendant's substantial assistance in the investigation or prosecution of another person who has committed an offense."
Department of Justice policy treats these filings with the same seriousness as pre-sentence cooperation pleadings. The Justice Manual provides that its procedures for substantial assistance pleadings apply to motions filed under Rule 35(b), and that "Such a filing is deemed for sentencing purposes to be the equivalent of a substantial assistance pleading." In plain terms, prosecutors document the facts and the justification behind each decision, and defense counsel should assume the decision will turn on a written record of what the cooperation actually produced.
The guideline behind cooperation credit: USSG 5K1.1
Rule 35(b) does not operate alone. Its companion is section 5K1.1 of the Guidelines Manual, titled Substantial Assistance to Authorities, which governs cooperation credit at the original sentencing. The Manual states: "Upon motion of the government stating that the defendant has provided substantial assistance in the investigation or prosecution of another person who has committed an offense, a sentence that is below the otherwise applicable guideline range may be appropriate." The same government-motion gatekeeper stands at both doors. The difference is timing. Section 5K1.1 rewards help given before sentencing. Rule 35(b) rewards help given after.
Section 5K1.1 also supplies the factors judges use to measure the help. The court sets the reduction for stated reasons that may include the significance and usefulness of the assistance, taking account of the government's evaluation; the truthfulness, completeness, and reliability of the information or testimony; the nature and extent of the assistance; any injury suffered or danger or risk of injury to the defendant or family because of the assistance; and the timeliness of the assistance. The Manual's commentary adds that substantial weight should go to the government's evaluation of the extent of the assistance, particularly where its value is hard to measure, and that the judge must state the reasons for the reduction, as 18 U.S.C. 3553(c) requires.
For the person hoping for a motion, this list is the practical checklist. Significance means the cooperation changed an outcome: an arrest, an indictment, a conviction, the recovery of money or drugs. Truthfulness means every statement held up. Timeliness means the help came when the government could still use it. And the government's evaluation carries special weight, which is why experienced counsel focus as much effort on documenting the assistance for the prosecutor as on arguing the motion to the judge.
How a Rule 35 reduction is argued to the judge
Once the government files the motion, the argument shifts to the size of the reduction, and here the general law of Federal Sentence Reduction rejoins the picture. The judge resentences against the backdrop of 18 U.S.C. 3553(a), the provision that governs every federal sentence. Its opening command sets the tone for the whole proceeding: "The court shall impose a sentence sufficient, but not greater than necessary, to comply with the purposes set forth in paragraph (2) of this subsection." The purposes that follow are the familiar ones: "to reflect the seriousness of the offense, to promote respect for the law, and to provide just punishment for the offense," to deter, to protect the public, and to provide needed training, care, or treatment.
A strong presentation therefore does two things at once. It proves the assistance with specifics: dates of meetings, agents worked with, testimony given, cases affected, risks taken. And it frames the person being resentenced: conduct in custody, employment history, family support, treatment completed, and a concrete plan for release. A presentation can use the guideline range as a starting point, the 5K1.1 factors to measure the cooperation, and the 3553(a) purposes to show the reduced sentence still reflects the seriousness of the original crime. Rule 35(b) itself does not list the factors a court must weigh. None of this guarantees any particular result. Judges vary widely in how much they discount for cooperation, and the same assistance can produce different reductions in different courtrooms. What a careful presentation can do is give the judge a clear record on which to exercise that discretion.
Two cautions belong here. First, cooperation carries real risks, including retaliation and exposure to further questioning, and the decision to cooperate should be made with counsel before any meeting with agents. Second, a Rule 35(b) motion can result in a modest reduction rather than the dramatic one families hope for, because the judge must still account for the seriousness of the offense that produced the original sentence. An honest assessment of both sides of that balance is part of what counsel is for.
What Rule 35 is not
Rule 35 is often confused with the other forms of post-conviction relief, and the distinctions matter because each path has its own deadline and its own standard. A direct appeal challenges legal errors from the trial or sentencing before the court of appeals. A motion under 28 U.S.C. 2255, addressed on our page about 28 U.S.C. 2255 motions, attacks the conviction or sentence on constitutional or jurisdictional grounds, such as ineffective assistance of counsel. Compassionate Release seeks reduction for extraordinary reasons such as serious illness, again under a different statute with different gates. Rule 35(a) is narrower than all of these: only obvious error, only within 14 days. Rule 35(b) is different in kind: only substantial assistance against another person, only on the government's motion. Filing the wrong motion in the wrong court wastes the one resource none of these doctrines gives back, which is time.
A note on penalties and predictions
The penalties discussed on this site are statutory maximums and guideline ranges, not predictions about any case. Congress sets the maximum. The Guidelines Manual computes a range. The judge imposes the sentence after weighing 18 U.S.C. 3553(a), and the facts of a case change everything: the quantity involved, the person's role, prior record, acceptance of responsibility, and cooperation. If you are deciding whether to cooperate or weighing a possible Rule 35 motion, speak with counsel early, document everything, and do not assume any outcome. The law opens specific doors at specific times. The work is recognizing which one is open for you and walking through it before it closes.