5K1: Understanding Substantial-Assistance Sentence Reductions in Federal Court

What 5K1 Refers To

In federal criminal practice, "5K1" is shorthand for United States Sentencing Guidelines § 5K1.1 — Substantial Assistance to Authorities. It is the provision the government uses to ask a federal judge to depart below the otherwise applicable guideline range when a defendant has provided substantial assistance in the investigation or prosecution of another person.

A related statute, 18 U.S.C. § 3553(e), gives the court limited authority to impose a sentence below an otherwise applicable statutory mandatory minimum on the same basis — but only on the government's motion.

What This Guide Covers

• What "5K1" means and where it comes from
• How a 5K1.1 motion works at sentencing
• How 5K1 differs from a post-sentencing Rule 35(b) reduction
• Why the practical custody impact of a reduction depends on BOP computation

What This Guide Does Not Do

• Provide legal advice or a recommendation about whether to cooperate
• Predict whether the government will file a 5K1 motion in a specific case
• Promise a specific reduction or release date
• Replace the BOP's official sentence computation

Who Files a 5K1 Motion?

The government does. USSG § 5K1.1 begins with the phrase "Upon motion of the government..." A defendant cannot file a 5K1 motion. Cooperation alone does not produce a motion — the prosecutor decides whether the assistance was substantial enough to warrant one.

What Courts Consider

USSG § 5K1.1 lists factors a court may consider, including:

• The court's evaluation of the significance and usefulness of the assistance
• The truthfulness, completeness, and reliability of the information provided
• The nature and extent of the assistance
• Any injury suffered, or danger or risk of injury to the defendant or family
• The timeliness of the assistance

The size of any departure is left to the court's discretion. Outcomes vary widely from case to case.

5K1 vs Rule 35(b)

Both reward substantial assistance. The key difference is timing.

• 5K1.1 — filed by the government before sentencing. The court applies any departure at the original sentencing hearing.
• Rule 35(b) — filed by the government after sentencing, typically within one year (with limited exceptions for later-occurring assistance). The court issues an amended judgment reducing a sentence already imposed.

For a deeper walk-through of how a post-sentencing reduction interacts with BOP release planning, see Understanding Rule 35(b) and Federal Release Date Timing.

Why a Reduction Does Not Always Mean the Same Number of Months Less Inside

Once the court imposes (or reduces) a sentence, the Bureau of Prisons computes the actual time served. That computation includes Good Conduct Time, First Step Act Earned Time Credits, RDAP-eligible programming, Residential Reentry Center placement, and home confinement. A 12-month reduction on paper does not always translate to 12 fewer months inside a federal facility. The Federal Sentence Calculator can help model these scenarios for educational purposes.

Records to Organize

• Judgment and Commitment Order and any amended judgments
• Plea agreement and any cooperation addendum
• Presentence Investigation Report (PSR)
• Sentence Monitoring Computation Data sheet, when available
• Documentation of programming, education, and work assignments