Federal Conspiracy Defense (18 U.S.C. § 371)

By Elizabeth Franklin-Best, Esq., and Christopher Zoukis, JD, MBA

Conspiracy is the most common charge in the federal system, and one of the most misunderstood. A person can be convicted of conspiracy without ever completing the underlying crime, without personally carrying out a single act, and sometimes without doing much more than agreeing. That breadth is why prosecutors charge it so often — and why a federal conspiracy lawyer should examine, early and closely, whether the government can actually prove an agreement at all.

Conspiracy work is a staple of our practice at Elizabeth Franklin-Best, P.C., because nearly every multi-defendant federal indictment we see leads with a § 371 count. Our principal attorney, Elizabeth Franklin-Best, has appeared in more than 330 federal proceedings — over 100 of them appeals across the circuits — and brings that federal-only focus to conspiracy cases in trial courts and on appeal nationwide; Best Lawyers in America named her its 2026 “Best Lawyer” in Appellate Practice. Conspiracy is a charge about agreement and intent, and we defend it by holding the government to proof of both.

This guide explains what federal conspiracy is, the structure of 18 U.S.C. § 371, what prosecutors must prove, the penalties involved, and how a defense is built. It is general legal information, not legal advice. If you have been named in an indictment or drawn into a conspiracy investigation, the starting point is a paid, one-hour initial consultation. This guide sits within our white-collar crime defense practice.

Quick Answer

Question	Answer
What is federal conspiracy?	An agreement between two or more people to commit a federal offense or to defraud the United States, followed by an overt act in furtherance of that agreement.
Is conspiracy a separate crime?	Yes. Conspiracy is its own offense. A person can be convicted of it even if the planned crime is never completed.
What must the government prove?	An agreement, the defendant’s knowing and voluntary decision to join it, and an overt act — all beyond a reasonable doubt.
What penalties can apply?	Under 18 U.S.C. § 371, up to 5 years in prison and fines; specialized conspiracy statutes can carry more.
What does an initial consultation cost?	One hour, paid — enough to review the indictment, identify your individual exposure, and outline a defense.

Key Takeaways

• Conspiracy punishes the agreement itself — the planned crime does not have to be completed, or even attempted to completion.
• The general conspiracy statute, § 371, requires an overt act by at least one conspirator; that act need not itself be illegal.
• Mere presence, knowledge, or association with wrongdoers is not a conspiracy — the government must prove a genuine agreement to join.
• Under the Pinkerton doctrine, a conspirator can be liable for foreseeable crimes that co-conspirators commit in furtherance of the agreement.
• Withdrawal is a recognized defense, but it requires affirmative action to disavow or defeat the conspiracy — and the defendant bears the burden of proving it.
• Conspiracy charges sweep in peripheral people, which makes the strength of the proof against each individual defendant the central question.

What Is Federal Conspiracy?

A federal conspiracy is an agreement between two or more people to commit a crime against the United States or to defraud it. The crime is the agreement. The law treats the decision of two or more people to join in unlawful purpose as itself dangerous enough to punish, separate from whatever they go on to do. That is why a defendant can be convicted of conspiracy even if the planned offense is never carried out — and why conspiracy is charged in a large share of federal indictments.

Conspiracy is also a charge that expands a case. It allows the government to try multiple defendants together, to introduce the statements of one conspirator against the others, and to hold a defendant responsible for conduct carried out by people they may barely know. For someone on the edges of an alleged scheme, that breadth is the danger. The defining question in most conspiracy cases is not what the group did — it is whether this particular defendant truly agreed to join it.

Section 371: Two Kinds of Conspiracy

The general federal conspiracy statute, 18 U.S.C. § 371, actually contains two distinct prohibitions:

• The offense clause — conspiracy to commit any specific offense against the United States, such as fraud, bribery, or theft.
• The defraud clause — conspiracy to defraud the United States. This reaches agreements to interfere with or obstruct a lawful government function through deceit, craft, or dishonest means, and it does not require that the government lose money.

The defraud clause is broad, but it is not boundless. The Supreme Court defined its reach a century ago in Hammerschmidt v. United States, 265 U.S. 182 (1924): to defraud the United States means to cheat the government out of money or property, or to obstruct a lawful governmental function “by deceit, craft or trickery, or at least by means that are dishonest” — no financial loss to the government required, but dishonest means always required. The clause is the basis for what practitioners call a “Klein conspiracy” — an agreement to impede the lawful functions of the Internal Revenue Service or another agency, a theory we cover in depth on our tax fraud defense page. Beyond § 371, federal law also contains many specialized conspiracy statutes — for drug offenses, for RICO, and for others — and some of them carry heavier penalties than § 371 and do not require an overt act. Identifying exactly which conspiracy statute the government has charged is the starting point of the defense.

What the Government Must Prove

To convict under § 371, the government must prove each of the following beyond a reasonable doubt:

• An agreement. Two or more people agreed to commit an offense against, or to defraud, the United States. The agreement can be unspoken and proven by circumstances, but it must be a real meeting of the minds.
• Knowing and voluntary participation. The defendant knew of the conspiracy’s unlawful purpose and chose to join it with the intent to further it.
• An overt act. At least one conspirator committed an overt act in furtherance of the conspiracy. The act itself does not have to be a crime — a single phone call or meeting can qualify.

The agreement element is where conspiracy cases are most often won. The law draws a firm line: mere knowledge that others are committing crimes, mere presence at the scene, and mere association with the people involved are not enough. A person can know about wrongdoing, even disapprove of it, and still not be a conspirator. The government must prove that the defendant actually agreed to join the unlawful objective — and that proof is frequently built on inference, which a defense can contest.

Applied insight. Conspiracy indictments often describe a sprawling scheme and then place a defendant somewhere near it. The defense’s task is to separate the individual from the crowd — to insist that the jury decide what this person knew and agreed to, not what the group as a whole did. Guilt by association is not a federal crime, and the case has to be tried that way.

Pinkerton Liability

One feature of conspiracy law makes it especially powerful for the government: the doctrine of Pinkerton v. United States, 328 U.S. 640 (1946). Under it, once a person is a member of a conspiracy, that person can be held criminally responsible for the substantive crimes committed by co-conspirators — even crimes the defendant did not commit, did not plan, and did not know about — so long as those crimes were committed in furtherance of the conspiracy and were a reasonably foreseeable consequence of it. Pinkerton itself drew the limits that still control: liability does not attach to acts outside the scope of the unlawful project or to consequences that could not reasonably be foreseen as a natural outgrowth of the agreement.

The practical effect is significant. A defendant who joined a conspiracy in a small way can face liability for the full scope of what the conspiracy did. That is why the defense fights hardest at the threshold — on whether the defendant joined the conspiracy at all, and, if so, on the limited scope of what that particular defendant agreed to. Foreseeability and the boundaries of the agreement become decisive, because they define how far Pinkerton liability can reach.

The Overt Act, Withdrawal, and the Statute of Limitations

Under § 371, the conspiracy is not complete until some member commits an overt act in furtherance of the agreement. The overt act is a low bar — a phone call, an email, a meeting, a bank deposit — and it need not be unlawful in itself. But it carries an important timing consequence: the five-year statute of limitations for a § 371 conspiracy runs from the last overt act committed in furtherance of the agreement, not from the moment the agreement was formed. A conspiracy that keeps acting keeps the limitations clock from starting, which is one reason the government frames schemes as long-running.

Withdrawal interacts with that clock. In Smith v. United States, 568 U.S. 106 (2013), the Supreme Court confirmed two hard rules: withdrawal requires affirmative action to disavow or defeat the conspiracy — passive non-participation is not enough — and the defendant bears the burden of proving it, even when withdrawal is combined with a limitations defense. The payoff, though, can be complete: a defendant who proves withdrawal more than five years before the indictment has a full defense to the conspiracy charge. For anyone who left a venture years before charges arrived, documenting that exit — when it happened, what was said, what was done — can be the whole case.

One caution: these rules describe § 371. Several specialized conspiracy statutes, including the drug-conspiracy provision, require no overt act at all, and the limitations analysis differs accordingly. The first task in any conspiracy case is confirming exactly which statute is charged.

How Conspiracy Cases Are Built — and Where They Crack

Conspiracy prosecutions are assembled from three characteristic sources. The first is cooperators — alleged co-conspirators who have pleaded guilty and testify in exchange for sentencing consideration, whose incentives the defense is entitled to put squarely before the jury. The second is the co-conspirator hearsay rule: statements made by one member of the conspiracy during and in furtherance of it can be admitted against the others, but only after the government establishes, by a preponderance, that the conspiracy existed and that the defendant was part of it — a threshold the defense can and should contest. The third is the investigative record built through grand jury subpoenas, agent interviews, and proffer sessions, stages we explain in our guide to the federal criminal process.

Each source carries risks for the people drawn into it. An interview answer that the government later calls untrue can become a false statements charge; grand jury testimony can generate a perjury count; and efforts to coordinate stories can be charged as obstruction of justice — or folded into the conspiracy itself as overt acts. That is why anyone touched by a conspiracy investigation, however peripherally, should have independent counsel before talking to anyone, including former colleagues.

Penalties for Federal Conspiracy

A conviction under § 371 carries a statutory maximum of five years in prison and a fine. There is one limit built into the statute: if the object of the conspiracy was only a misdemeanor, the punishment for the conspiracy cannot exceed the maximum for that misdemeanor. But § 371 is not the only conspiracy statute. Many specialized conspiracy provisions — including those for drug offenses and RICO — are punished as severely as the underlying substantive crime, which can mean far more than five years. At sentencing, a § 371 count is generally scored under U.S.S.G. § 2X1.1 by reference to the guideline for the object offense — and where the conspirators neither completed nor were on the verge of completing the acts needed for the substantive crime, a three-level reduction can apply. Whether a scheme was that close to completion is a fact-specific fight worth having.

Conspiracy also affects sentencing in subtler ways. Because a conspiracy count can hold a defendant accountable for the conduct of the whole agreement, the loss amounts, drug quantities, or other measures that drive the Sentencing Guidelines may be calculated on the basis of the entire conspiracy rather than the defendant’s individual acts — subject to limits tied to the scope of what the defendant agreed to and could foresee. That makes the scope of the agreement a sentencing issue as well as a guilt issue. Our federal sentencing practice addresses those calculations.

Applied insight. In a conspiracy case, the scope of the agreement is litigated twice — once on guilt and again at sentencing. Establishing that a defendant agreed to something narrow, and could foresee only so much, is not a single argument; it is a theme that has to run through the entire defense.

Defending a Conspiracy Case

The central conspiracy defense is the absence of agreement. Because mere presence, knowledge, and association are not enough, a defense may show that the defendant was a bystander, an unwitting participant, or someone whose dealings with the group were innocent or arm’s-length. Where the government’s proof of agreement rests on inference, the defense presses the gap between knowing about a scheme and joining it.

Other defenses are structural. Withdrawal is a recognized defense: a defendant who took affirmative steps to disavow or defeat the conspiracy can cut off liability for later acts and start the statute of limitations running — though the defendant bears the burden of proving it, and passive non-participation does not count. A variance defense applies when the government charges one large conspiracy but the proof shows only smaller, separate ones, leaving a defendant prejudiced by evidence of crimes they had nothing to do with. This single-versus-multiple-conspiracy question is governed by Kotteakos v. United States, 328 U.S. 750 (1946), where the Supreme Court reversed convictions because the evidence revealed “separate spokes meeting in a common center” — independent groups dealing with one central figure — “without the rim of the wheel to enclose the spokes.” Courts ask whether the alleged conspirators shared a common goal, depended on one another, and overlapped in membership; absent a connecting “rim,” a hub-and-spoke indictment describes several conspiracies rather than one, and trying them together risks the “transference of guilt” Kotteakos condemned. That distinction is both a guilt-stage defense and a powerful argument for severance. The statute of limitations, the sufficiency of the overt act, and whether the charged object is even a federal offense are all fair targets. We examine the indictment and the evidence defendant by defendant, and we keep the jury focused on individual proof. Outcomes in conspiracy cases turn on too many variables for honest guarantees, and we offer none; what you can count on is that every inference the government calls an “agreement” will have to survive our scrutiny first.

Why Work With Elizabeth Franklin-Best, P.C.

Multi-defendant conspiracy litigation rewards lawyers who can hold a complex record together and still argue one client’s corner of it. That combination — command of the whole and advocacy for the individual — is what Elizabeth Franklin-Best built this firm around. A federal-only practitioner admitted before the United States Supreme Court and every federal circuit court of appeals, she appears nationwide by pro hac vice admission, has handled more than 100 federal appeals arising from exactly these kinds of multi-defendant records, wrote Reversing Your Criminal Conviction, and holds a 2026 Chambers USA ranking in Litigation: White-Collar Crime & Government Investigations.

Conspiracy cases are won on careful, individualized analysis — separating one defendant’s actual agreement from the conduct of a crowd. That is the kind of work our practice is built around. In these cases our first deliverable is a defendant-specific map of the indictment: which overt acts involve our client, which co-conspirator statements the government will offer, and where the proof of agreement actually comes from. This guide is part of our broader white-collar crime defense practice.

Talk With a Federal Conspiracy Lawyer

If you have been named in a federal conspiracy indictment, or learned that you are part of a conspiracy investigation, the decisions ahead — about cooperation, about a joint defense, about your own exposure — are consequential, and they tend to arrive quickly. In a paid, one-hour initial consultation, we look at where you actually sit in the government’s theory and tell you what we would do about it, starting now.

Frequently Asked Questions