Part of our complete guide to Rule 35(b) sentence reductions in federal court.
Rule 35(b) is a provision of the Federal Rules of Criminal Procedure that permits a federal court to reduce a defendant’s sentence after sentencing when the defendant has provided substantial assistance to the government in investigating or prosecuting another person.
Unlike most sentence reductions, a Rule 35(b) reduction begins with the government. The defendant cannot file a Rule 35(b) motion on his own. Instead, the prosecutor must decide that the defendant’s assistance was sufficiently valuable to justify asking the court for a reduction.
When the government files a Rule 35(b) motion, the sentencing judge may reduce the sentence if the judge concludes that a reduction is appropriate. The amount of the reduction varies from case to case. Some reductions are relatively modest, while others may result in substantial decreases in the defendant’s sentence.
Rule 35(b) is often described as the post-sentencing counterpart to a substantial-assistance departure under Section 5K1.1 of the United States Sentencing Guidelines. The difference is largely a matter of timing. A Section 5K1.1 motion is filed before or at sentencing. A Rule 35(b) motion is filed after sentencing.
For example, a defendant may provide information before sentencing, but the government may not know whether that information will prove useful until months later. In another case, a defendant may begin cooperating only after sentencing by providing information about criminal activity, identifying other participants, testifying in court, assisting investigators, or helping locate criminal proceeds. In those circumstances, Rule 35(b) may provide a mechanism for the government to request a sentence reduction.
It is important to understand that Rule 35(b) does not guarantee a reduction. Cooperation alone does not automatically result in a lower sentence. The government must determine that the assistance was substantial, and the government must choose to file a motion requesting relief. Even after a motion is filed, the judge retains discretion to decide whether a reduction should be granted and how large that reduction should be.
Many defendants and families mistakenly believe that Rule 35(b) operates like an appeal or a request for compassionate release. It does not.
A Rule 35(b) motion is not based on legal error at sentencing. It is not based on medical conditions, age, or family circumstances. It is based on one thing: substantial assistance provided to the government after sentencing.
Rule 35(b) Compared to Other Forms of Relief
Because federal inmates often hear about several different types of post-conviction relief, it is helpful to understand the differences.
- Appeal. An appeal challenges legal errors that may have occurred during the criminal proceedings. Appeals focus on issues such as evidentiary rulings, jury instructions, sentencing errors, or constitutional violations.
- Section 2255 Motion. A motion under 28 U.S.C. § 2255 allows a defendant to challenge the legality of a conviction or sentence. Common claims include ineffective assistance of counsel and constitutional violations.
- Compassionate Release. Compassionate release focuses on extraordinary and compelling circumstances, such as serious medical conditions, advanced age, or certain family situations.
- Rule 35(b). Rule 35(b) focuses exclusively on substantial assistance provided to the government after sentencing.
Because these forms of relief serve different purposes, a defendant may qualify for one type of relief without qualifying for another.
The Key Takeaway
The most important thing to remember is this:
Rule 35(b) is a tool that allows the government to seek a sentence reduction for a defendant who provides substantial assistance after sentencing. The process begins with the government, not the defendant, and the ultimate decision rests with the sentencing judge.
The next question is often the most important one: what exactly counts as “substantial assistance”? We address that issue in detail in our guide to substantial assistance under Rule 35(b).

