A federal conspiracy charge under 18 U.S.C. 371 must generally be indicted within five years, and that is the short answer to the 18 U.S.C. 371 statute of limitations question. The catch is when the five years begin to run: not when the agreement was formed, and not when any particular defendant last participated, but when the last overt act in furtherance of the conspiracy occurred. For conspiracies whose target crime carries its own longer limitations period, the window stretches to six, seven, or ten years, and several tolling rules can pause the clock even after the last act.
When the Five-Year Clock Starts
The default limitations period for non-capital federal offenses is five years under 18 U.S.C. 3282, and Section 371 conspiracies fall under that baseline unless the object offense triggers something longer.1Office of the Law Revision Counsel. 18 USC 3282 – Offenses Not Capital
For most crimes the clock starts on the date the offense was committed. Conspiracy is different. Because it is treated as a continuing offense, the clock starts on the date of the last overt act taken to advance the scheme. The Supreme Court set this rule in Fiswick v. United States, holding that the limitations period runs from the last overt act during the existence of the conspiracy.
Any act by any member that pushes the conspiracy forward resets the clock for everyone still in the agreement, including participants who have gone quiet. The act can be small. A final payment, a routine deposit of proceeds, a phone call setting up a meeting, or the filing of a fraudulent form all qualify if they advance the conspiratorial objective rather than merely tidying up something already finished. A conspiracy ends when its central goal is achieved, when the participants abandon it, or when everyone withdraws, and the countdown begins on whichever comes last. Prosecutors will identify the latest defensible overt act to maximize their window, which is why conspiracy indictments often recite long timelines of activity.
An indictment returned within the five-year window satisfies the statute even if it is sealed. What matters is when the grand jury votes to return it, not when it becomes public.
When the Window Is Longer Than Five Years
A Section 371 conspiracy borrows the limitations period of its object offense when that period is longer than five years. Several categories of conspiracy get more time as a result.
- Tax offenses carry a six-year limitations period, which applies to Section 371 conspiracies aimed at evading or defeating any federal tax.2Office of the Law Revision Counsel. 26 USC 6531 – Periods of Limitation on Criminal Prosecutions
- Major fraud against the United States, involving federal grants, contracts, subsidies, loans, or other assistance of $1 million or more, can be charged within seven years.3Office of the Law Revision Counsel. 18 USC 1031 – Major Fraud Against the United States
- Financial institution offenses, including bank fraud, misapplication of bank funds, and false bank entries, as well as wire fraud and mail fraud that affect a financial institution, carry a ten-year period.4Office of the Law Revision Counsel. 18 USC 3293 – Financial Institution Offenses
- Offenses involving the sexual or physical abuse, or kidnapping, of a child under 18 have no limitations period during the life of the child, or ten years after the offense, whichever is longer. A conspiracy targeting such an offense inherits that window.5Office of the Law Revision Counsel. 18 USC 3283 – Offenses Against Children
A single conspiracy with multiple objects can trigger different limitations periods for different counts in the same indictment.
Tolling Rules That Pause the Clock
Three statutory mechanisms can suspend the limitations period after the last overt act.
Fugitive Status
Under 18 U.S.C. 3290, no limitations period runs against a person who is fleeing from justice.6Office of the Law Revision Counsel. 18 USC 3290 – Fugitives From Justice The statutory language is absolute, and courts have read “fleeing from justice” broadly enough that leaving the jurisdiction is not required. Hiding with the intent to avoid prosecution can qualify, and the government carries the burden of proving that intent.
Foreign Evidence
When prosecutors formally request evidence located abroad, a court can suspend the limitations period under 18 U.S.C. 3292 while that request is pending. Total suspension cannot exceed three years, and if the foreign government produces the evidence before the original deadline would have expired, the extension is capped at six months beyond that deadline.7Office of the Law Revision Counsel. 18 USC 3292 – Suspension of Limitations to Permit United States to Obtain Foreign Evidence This comes up often in international fraud and money laundering conspiracies.
Wartime Suspension
When the United States is at war or Congress has authorized the use of military force, the limitations period is suspended for certain fraud-related offenses, including fraud against the government and crimes tied to military contracts and procurement. The suspension runs until five years after hostilities end.8Office of the Law Revision Counsel. 18 USC 3287 – Wartime Suspension of Limitations Since use-of-force authorizations can remain in effect for years, this can extend the window substantially for fraud conspiracies tied to government contracts.
Starting Your Own Clock by Withdrawing
An individual conspirator can begin their own five-year clock by withdrawing from the conspiracy, even if the others carry on. Withdrawal is not passive. In Smith v. United States (2013), the Supreme Court held that withdrawal requires an affirmative act, either telling co-conspirators you are out or disclosing the conspiracy to law enforcement, and that the defendant bears the full burden of proving it.9Legal Information Institute. Smith v. United States, 568 U.S. 106
The government does not have to disprove withdrawal. It only has to show the conspiracy extended past the limitations cutoff. If you claim you left earlier, proving that is your problem. This burden-shifting is unusual in federal criminal law, and it makes the withdrawal defense hard to win in practice.
Why Concealment Usually Doesn’t Extend the Clock
Prosecutors sometimes argue that a conspiracy continued for years past its central acts because participants worked to hide what they had done. The Supreme Court rejected that approach in Grunewald v. United States (1957), holding that once a conspiracy achieves its main goal, extra years cannot be tacked on simply because the conspirators tried to cover their tracks. A conspiracy to commit fraud does not automatically include a subsidiary conspiracy to hide the fraud afterward.10Justia. Grunewald v. United States, 353 U.S. 391
The Court’s reasoning was practical. Every conspirator tries to avoid getting caught, and treating concealment as part of the conspiracy would effectively eliminate the statute of limitations for conspiracy charges.
There is a narrow exception. If the original agreement specifically included concealment as one of its objectives, then acts of concealment count as overt acts that keep the clock running. The indictment must charge that expressly, and courts examine whether the evidence actually supports an up-front agreement to conceal rather than a prosecutor’s later attempt to stretch the timeline.10Justia. Grunewald v. United States, 353 U.S. 391
Raising the Defense
A limitations challenge is raised through a pretrial motion to dismiss under Rule 12 of the Federal Rules of Criminal Procedure, which lets a defendant raise any defense the court can resolve without a trial and specifically recognizes the statute of limitations as one of them.11Legal Information Institute. Federal Rules of Criminal Procedure, Rule 12 – Pleadings and Pretrial Motions
Raise it promptly. Rule 12 requires certain defenses to be raised before trial or they are forfeited, though courts have some discretion to consider late-raised claims for good cause. This is one of the first things a federal defense attorney evaluates after reviewing an indictment.
A separate but related argument comes from the Fifth Amendment’s Due Process Clause. Even when the limitations period has not expired, an indictment can be dismissed if the government delayed filing charges for an unreasonably long time. You have to show two things: the delay actually harmed your defense through lost evidence, unavailable witnesses, or memory loss beyond ordinary fading, and the government delayed for an improper reason rather than continuing to investigate. Courts give prosecutors wide latitude for investigative delay, so this argument is harder to win than a straightforward time-bar defense.