The starting rule: the sentence is final
The statute states the rule in one sentence: "The court may not modify a term of imprisonment once it has been imposed except that" in the situations the law then lists. Finality is the default. A federal judge cannot revisit a prison sentence out of second thoughts, sympathy alone, or a general sense that less time would be fair. Shortening happens only through an open door, and there are three.
First, compassionate release under section 3582(c)(1)(A), for extraordinary and compelling reasons. Second, a retroactive guideline change under section 3582(c)(2), where the Sentencing Commission later lowered the range behind the sentence. Third, correction or reduction under Rule 35 of the Federal Rules of Criminal Procedure, which covers clear error caught within days and cooperation credit sought on the government motion. Each door has its own movant, its own test, and its own limits, and confusing them wastes the little time these motions allow. Our federal sentencing page explains how the sentence was built in the first place, which is the baseline every reduction motion is measured against.
First path: compassionate release
Compassionate release accepts the conviction and asks the court that imposed the sentence to shorten the prison term because something extraordinary now warrants it. The authority is section 3582(c)(1)(A), and the Sentencing Commission policy statement at USSG section 1B1.13 spells out what counts.
There is a gate before the courthouse door. The motion can come from the Director of the Bureau of Prisons, or from the defendant after he or she has "fully exhausted all administrative rights to appeal a failure of the Bureau of Prisons to bring a motion on the defendant's behalf or the lapse of 30 days from the receipt of such a request by the warden of the defendant's facility, whichever is earlier." In plain terms, first ask the warden in writing, keep proof of when the warden received it, and file in court only after appeals are exhausted or 30 days pass, whichever comes first.
If the motion gets through the gate, the court needs three findings. The statute requires "extraordinary and compelling reasons warrant such a reduction," or in the alternative a narrow age and time served combination for certain long sentences. The guideline restates the test as three parts: extraordinary and compelling reasons warrant the reduction, "the defendant is not a danger to the safety of any other person or to the community," and the reduction fits the policy statement. The court must also consider the sentencing factors "to the extent that they are applicable," which the later section of this page explains.
The policy statement lists six groups of qualifying reasons. Medical circumstances include terminal illness, which it describes as "suffering from a terminal illness (i.e., a serious and advanced illness with an end-of-life trajectory)," with no specific life expectancy prognosis required. They also include serious conditions that destroy the ability to provide self-care in prison with no expected recovery, needed care the prison is not providing, and defined infectious disease or public health emergency situations. Age covers defendants at least 65 with serious age driven decline who have served at least 10 years or 75 percent of the term, whichever is less. Family circumstances cover the death or incapacitation of a child's caregiver, an incapacitated spouse or partner, or an incapacitated parent, where the defendant would be the only available caregiver, plus similar situations for other close family. Custody abuse covers defined sexual or physical abuse by correctional staff that is established through a criminal, civil, or administrative finding. Two more groups close the list. Other reasons of similar gravity to the listed ones can qualify alone or combined with them. And an unusually long sentence can count where the defendant has served at least 10 years and a change in the law would produce a gross disparity with the likely sentence today, after full consideration of the individual case.
Two limits matter most in practice. A change in the law alone generally cannot create eligibility, except through that unusually long sentence path, though it can affect how large a justified reduction becomes. And "rehabilitation of the defendant is not, by itself, an extraordinary and compelling reason," though rehabilitation combined with other reasons can support relief. Good conduct inside is worth documenting for the danger and sentencing factor analysis, but it cannot carry the motion alone. Our compassionate release page walks through the warden step, the qualifying reasons, and how courts decide, in full detail.
Second path: the guideline range was later lowered
Sometimes the law behind the sentence changes after sentencing. When the Sentencing Commission lowers a guideline range and makes that change retroactive, a defendant sentenced under the old range can ask the court to conform the sentence to the new one. The statute covers "the case of a defendant who has been sentenced to a term of imprisonment based on a sentencing range that has subsequently been lowered by the Sentencing Commission pursuant to 28 U.S.C. 994(o)." The motion can come from the defendant, from the Director of the Bureau of Prisons, or from the court itself, since the law permits reduction "upon motion of the defendant or the Director of the Bureau of Prisons, or on its own motion."
This path has the hardest arithmetic of the three, governed by the policy statement at USSG section 1B1.10. Eligibility turns on listed amendments only. A reduction is not consistent with the policy statement, and therefore not authorized, if none of the amendments in the policy statement list applies to the defendant, or if a listed amendment applies but does not actually lower the range because something else, like a statutory minimum, holds it in place. A new amendment that lowers ranges going forward but was never listed for retroactive use helps future defendants, not people already sentenced.
When eligibility exists, the court recalculates in a disciplined way: "the court shall substitute only the amendments listed in subsection (d) for the corresponding guideline provisions that were applied when the defendant was sentenced. All other guideline application decisions remain unaffected." Everything about the original sentencing that the amendment did not touch stays frozen. The court cannot revisit old factual disputes, role findings, or criminal history scoring through this motion. It swaps in the new provision and nothing else.
Two floors then cap how far the sentence can fall. The reduced term generally cannot go below the bottom of the amended range. An exception exists where the original sentence sat below the old range on a government motion for substantial assistance. There the court can give a comparable proportional cut below the new range. And in no case can the result go below time already served: "In no event may the reduced term of imprisonment be less than the term of imprisonment the defendant has already served."
Within those walls the court exercises judgment. It must consider the applicable sentencing factors, "shall consider the nature and seriousness of the danger to any person or the community" that a reduction might pose, and "may consider post-sentencing conduct of the defendant" since the sentence was imposed. Danger evidence and the prison record therefore shape the outcome even when the arithmetic favors relief.
The most recent large scale example is Amendment 821. One part limited the criminal history impact of status points, the extra points for committing the offense while under another sentence. The other created a two level reduction for certain defendants with zero criminal history points whose offense lacked specified aggravating factors. The policy statement carries a timing instruction for these: "The court shall not order a reduced term of imprisonment based on Part A or Part B, Subpart 1 of Amendment 821 unless the effective date of the court's order is February 1, 2024, or later." That date has passed, so eligible motions under those provisions can now be granted, but the instruction shows how retroactivity orders carry their own effective dates that must be honored.
Third path: Rule 35
Rule 35 of the Federal Rules of Criminal Procedure holds two very different tools that share a number. The first is fast and narrow. "Within 14 days after sentencing, the court may correct a sentence that resulted from arithmetical, technical, or other clear error." This is the typo and math mistake rule, plus errors so clear they are obvious on the face of the sentence. It is not a second argument about what the sentence should have been. And the clock matters in a specific way, because for this rule sentencing has a defined meaning: as used in the rule, it "means the oral announcement of the sentence." The 14 days run from what the judge said in the courtroom, not from the later written judgment.
The second tool is the cooperation cut. "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." Three features define it. Only the government can bring the motion, so the defendant cannot file it alone. The assistance must come after sentencing, though the court may also weigh help given before sentencing when judging value. And "When acting under Rule 35(b), the court may reduce the sentence" even to a level below a statutory minimum, which makes this one of the few routes under a floor like the ones on our mandatory minimum page.
Later motions, more than a year after sentencing, are allowed only in three defined situations: information the defendant did not know until at least a year after sentencing, information given within the year that only became useful later, or information whose usefulness could not reasonably have been anticipated until later and was promptly provided once it became apparent. Each turns on timing the defendant must prove, which is why cooperation discussions should involve counsel from the start rather than after the year has run. Our Rule 35 motion page covers both halves of the rule and the substantial assistance standard in detail.
What the judge weighs every time
Compassionate release and guideline reductions run through the sentencing factors, to the extent they apply. Section 3553(a) directs that "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." A reduction motion asks the court to apply that same measure to less time, and the factors shape most decisions on this page.
The court looks at "the nature and circumstances of the offense and the history and characteristics of the defendant," then at the purposes of the sentence: "to reflect the seriousness of the offense, to promote respect for the law, and to provide just punishment for the offense," "to afford adequate deterrence to criminal conduct," "to protect the public from further crimes of the defendant," and to provide needed training, care, and treatment. It also considers the kinds of sentences available, the guideline range and the Commission policy statements, the need to avoid unwarranted disparities among similar defendants, and the need to provide restitution to victims. No single factor controls. A strong medical showing still faces the seriousness of the offense and the danger analysis. A favorable recalculation still faces deterrence and disparity. The motion that wins is the one that walks through each applicable factor honestly instead of leaning on one.
Two cautions belong here. The penalties and ranges described on this site are statutory maximums or guideline calculations, not predictions about any case. A retroactive amendment that lowers a range does not promise a lower sentence, because the judge can deny any discretionary reduction the law permits. And the facts of a case change everything. Two defendants with the same charge and the same amendment can get different answers based on conduct, history, danger, and the sentencing factors.
What a reduction is not
A reduction leaves the conviction standing. It shortens prison time without disturbing the guilty plea or verdict, which is what separates it from its two closest neighbors. A direct appeal asks a higher court to review errors from the trial court, on a short deadline of its own. A 2255 motion asks the sentencing court to throw out the judgment itself on narrow legal grounds. A person who believes the conviction is legally broken needs one of those instead of, or in addition to, a reduction motion, and the deadlines for each run independently, so waiting on one path can kill another.
It also helps to keep the presentence report in view. That report drove the original guideline calculation, and in a retroactive amendment case the court freezes everything except the amended provision. Errors in the report that went unchallenged at sentencing generally stay frozen too, which is one more reason the original sentencing hearing deserves full effort rather than reliance on a later fix.
How these motions are argued
Eligibility comes first, before storytelling. Counsel checks the threshold question for the chosen door. For compassionate release, was the warden step completed and does at least one qualifying reason fit. For a guideline change, is the amendment on the retroactive list and does it actually lower this defendant's range. For Rule 35, is the 14 day window still open for clear error, or will the government bring a cooperation motion. A motion filed through the wrong door fails without reaching the merits, and a defective filing can burn time a sick or aging defendant does not have.
The record comes next. The judgment, the plea agreement if there was one, the sentencing transcript, and the presentence report set the baseline. Medical records with specific diagnoses and functional limits, family evidence showing no other caregiver, proof of the warden request date, and the amended range calculation each prove one element of the test. Vague assertions without paper lose to a prosecutor response built on the file.
Then the argument ties each fact to the legal test and to the sentencing factors. Danger to the community gets its own evidence, not a passing mention, because the guideline demands it in two of the three paths. Post sentencing conduct is documented with certificates, work records, and disciplinary history, good and bad, since the court will see the full file anyway. Disparities are addressed head on by showing what similarly situated defendants received. And relief is framed within the limits that apply: for a guideline reduction, generally at or above the amended range bottom, and never below time already served, consistent with the policy statements.
If someone you love is serving federal time, start with the threshold question, not the strongest emotion. Identify which door fits, confirm the gate is open, and gather the paper that proves each element. The law gives judges real power to shorten sentences, but only inside the lines Congress and the Commission drew. A motion that respects those lines, proves each requirement, and speaks to every applicable sentencing factor gives the court something it can grant. The facts of the case change everything else, so early advice before any window closes is worth more than the strongest argument filed too late.