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When You Should NOT Enter a Proffer Agreement
The Proffer You Should Not Have Taken
The proffer session that destroys a defense is not the one where the client lies. It is the one where the client tells the truth to a government that did not need to hear it.
Most articles on this subject begin with a definition. A proffer agreement, sometimes called a “queen for a day” letter, is a written contract between a defendant and federal prosecutors permitting the defendant to provide information under limited immunity. That definition is correct, and it is insufficient for the decision in front of you. The question is not what a proffer agreement is; the question is when one should not exist at all.
Federal Rule of Evidence 410 was designed to encourage plea negotiations by protecting statements made during those negotiations from use at trial. The proffer agreement sits adjacent to that protection, but it is not the same instrument, and the waivers it contains carve exceptions that Rule 410 alone would not permit. Every proffer letter we have reviewed in this district contains a waiver of the protections that Kastigar v. United States established for immunized testimony: the prohibition on derivative use, the burden on the government to prove independent sourcing. The letter waives these before the first question is asked. I wrote the initial draft of this piece on a Wednesday in late February, and even now, reviewing it under better light, the central claim holds: the circumstances in which a proffer agreement should be declined outnumber the circumstances in which one should be signed.
When the Government’s Evidence Does Not Require Your Assistance
One refusal is simpler than the rest.
If the government’s evidence against you is weak, incomplete, or circumstantial, a proffer session does not improve your position. It improves theirs.
Prosecutors do not extend proffer invitations as courtesies. The invitation arrives because the government perceives a gap in its case. That gap might involve an uncooperative witness, a missing document, or a theory of liability that requires your own words to complete. When the evidence is strong, the government does not need you to confirm what it already possesses. When the evidence is thin, the government needs you more than you need the government, and the proffer letter inverts that dynamic the moment you sign it.
The first letter from the U.S. Attorney’s Office tends to arrive when the business is already in difficulty, when cash flow has contracted and when the owner has already spoken to someone (a partner, an accountant, a former colleague who once went through something similar) who suggested the conversation was inevitable. The instinct is to cooperate because cooperation feels like control, but what it offers is disclosure, not control.
Consider the client who receives a target letter in a wire fraud investigation. The government has financial records and email correspondence, but the records are ambiguous and the emails require interpretation. The client possesses the interpretation the government lacks. A proffer session provides that interpretation under oath, in a room with agents trained to identify not just admissions but investigative leads. Three cases in this district over the past two years involved defendants who proffered when the government’s documentary evidence, on its own, would not have survived a motion for summary judgment. The proffer supplied what the documents could not.
What the client perceives as an opportunity to explain is, from the government’s perspective, an opportunity to listen. The explaining party assumes the risk in that exchange, and the benefit flows in the other direction.
We evaluate every proffer invitation by asking a question the government will not answer: what does the prosecution possess without our client’s participation? If the answer is a case that proceeds to indictment regardless, cooperation may reduce sentencing exposure and a proffer becomes a rational instrument. If the answer is a case that weakens or stalls without cooperation, the proffer is the prosecution’s lifeline, not the defendant’s. This distinction is not always clear. Federal investigations are opaque by design, and the government is under no obligation to reveal the strength of its evidence before the proffer session begins. The assessment requires inference: what charges have been discussed, what documents have been subpoenaed, what co-defendants have already cooperated and on what terms. In cases where those signals suggest the government is still constructing its theory, the silence protected by the Fifth Amendment is worth more than anything the proffer letter promises.
There is a particular variety of pressure that operates on a person who has been told they are the subject of a federal investigation but who has not yet been charged. The pressure does not come from the government directly, or not only from the government. It comes from the waiting. The phone call that has not arrived. The business that continues to operate under conditions the owner cannot assess. The proffer letter, when it comes, can feel like resolution. What it initiates is something different: a disclosure from which there is no procedural retreat.
Derivative Use and the Kastigar Waiver
In Kastigar v. United States, the Supreme Court held that use and derivative use immunity is coextensive with the Fifth Amendment privilege against self-incrimination. The government may compel testimony under a grant of immunity, but it bears the burden of proving that any evidence subsequently used against the witness derives from sources independent of the compelled testimony. That framework protects the witness.
The proffer agreement dismantles it.
Standard proffer letters in most U.S. Attorney’s Offices contain a clause permitting the government to pursue investigative leads suggested by the defendant’s statements. The evidence recovered through those leads is admissible. The Kastigar burden, which would otherwise require the government to demonstrate independent sourcing at a taint hearing, is waived by the letter itself. In the Eleventh Circuit, United States v. Pielago confirmed that proffered information could generate independent evidence usable against the defendant. Whether every circuit enforces the derivative use waiver with equal consistency is a question I am less certain about than the preceding sentences might suggest, though the tendency across the circuits that have addressed it has been to favor the government’s reading.
The practical consequence operates the way a fire alarm functions in a building where every exit has been sealed: the mechanism exists, it activates on schedule, and it changes nothing about the outcome. You mention a meeting during the proffer. The government subpoenas records from that meeting. Those records contain information you did not know existed. That information is admitted at trial. Your own words constructed the path to your conviction, though your words themselves were never entered into evidence.
The second waiver concerns impeachment. If the defendant’s testimony at trial, or any evidence or argument offered on the defendant’s behalf, is inconsistent with statements made during the proffer, the government may introduce the proffer statements in rebuttal. The Second Circuit upheld this provision in United States v. Velez, finding the waiver enforceable where it was entered knowingly and voluntarily. The effect is architectural: the proffer does not merely expose the defendant to derivative evidence. It constrains the entire trial defense to a posture consistent with whatever was said in the government’s conference room. Any departure, any inconsistency perceived by the prosecution, opens the door to the proffer itself.
Whether the court intended Velez to produce this chilling effect on trial strategy, or merely failed to prevent it, is a question worth considering.
Overlapping Jurisdictions
A proffer agreement binds the office that signs it. It does not bind the state attorney general, the county prosecutor, the SEC, the IRS Criminal Investigation division, or any foreign authority conducting a parallel investigation into the same conduct.
This gap has widened. State, federal, and foreign enforcement actions increasingly overlap, and information shared during a federal proffer session (which, it should be noted, the government may share with other agencies under the terms of most standard letters, and which even those letters that restrict sharing cannot always control once the information enters a multi-agency task force environment) can surface in proceedings where the proffer’s protections do not apply. The defendant who proffers to the U.S. Attorney’s Office in the Southern District may discover that the same information has reached a state attorney general with independent prosecutorial authority and no obligation to honor the federal agreement.
The Lankler Siffert team’s 2025 analysis in Law360 identified this as the overlooked risk in contemporary proffer practice. The observation is correct. The risk is structural, and it grows in proportion to the complexity of the underlying investigation.
Before any proffer session, defense counsel must identify every jurisdiction with potential prosecutorial interest in the conduct at issue. If the list exceeds the single office offering the letter, the protections offered are partial at best.
The Constraint on Trial Strategy
In the Southern District, the standard proffer agreement permits the government to use proffered statements to rebut any evidence or arguments offered by or on behalf of the defendant at any stage of prosecution, including sentencing. The rebuttal trigger is broad. It extends to arguments raised by the court on its own initiative.
The practical effect is that a defendant who has proffered and then proceeds to trial occupies a narrower corridor than a defendant who has not. Trial counsel cannot introduce testimony, cross-examine witnesses, or advance theories that contradict the proffer statements without opening the door to those statements. In Velez, the defendant chose not to introduce anticipated defense testimony precisely because doing so would have activated the waiver provision. He was convicted. The jury never heard the testimony his lawyer had prepared to present.
The sentencing implications are similarly constricting. Under the federal sentencing guidelines, relevant conduct includes all criminal activity that was part of the same course of conduct or common scheme, even if uncharged. Admissions made during a proffer can expand the relevant conduct calculation. The proffer letter in most districts does not protect against this use at sentencing. The defendant who enters a proffer expecting to discuss a single transaction may discover that the government’s questions extend across years and across conduct that was never the subject of investigation, and that the answers now inform the guidelines calculation.
This is procedural territory, and there is not much to say about it that is not already mechanical. The constraint is real, and for most defendants it remains invisible until trial preparation begins.
Before the Letter Arrives
The decision whether to proffer is not a legal question alone. It is a question about what the government knows, what the government needs, and whether the distance between those two points can be closed without your participation.
In many cases the answer is yes. The government will close that distance through other cooperators, through documents, through the slow accumulation of evidence that federal investigations are designed to produce. Your silence, in those cases, is not an obstacle the government cannot overcome. It is a right the Constitution provides precisely because the alternative, compelled disclosure without adequate protection, was the condition the Fifth Amendment was drafted to prevent.
In every case we evaluate, the proffer question is the first question, not the last. We examine it before charges, before plea discussions, before the scope of the investigation has been defined by the government’s terms. The analysis begins with what we can determine about the government’s evidence through lawful means, and it proceeds toward a recommendation that weighs cooperation against silence on the specific facts of the matter, not on a general presumption that cooperation is preferable. A consultation is where that analysis begins. It costs nothing and it assumes nothing. It is the first conversation in a process that, conducted with sufficient care, preserves every option the law permits.