Respondent Mezzanatto faced federal narcotics charges arising from a methamphetamine transaction. Seeking to explore cooperation, he met with prosecutors for a plea/proffer discussion. Before the meeting, the government required a written proffer agreement in which Mezzanatto expressly waived the protections of Federal Rule of Evidence 410 and Federal Rule of Criminal Procedure 11(e)(6) to the extent of allowing the government to use any of his statements for impeachment if he later testified inconsistently at trial. During the proffer session, Mezzanatto made statements indicating knowledge of the drug transaction that were inconsistent with his later trial testimony. Plea discussions broke down. At trial, Mezzanatto took the stand and offered an exculpatory account that conflicted with his earlier proffer statements. Over defense objection invoking Rule 410 and Rule 11(e)(6), the district court allowed the prosecution to use the proffer statements solely to impeach his credibility. The jury convicted. On appeal, the Ninth Circuit reversed, holding that the rules' exclusionary protections could not be waived for impeachment purposes. The Supreme Court granted certiorari and reversed the Ninth Circuit.
May a criminal defendant waive the protections of Federal Rule of Evidence 410 and Federal Rule of Criminal Procedure 11(e)(6) so that statements made during plea discussions can be used to impeach the defendant's testimony at trial?
Personal rights and evidentiary protections are presumptively waivable absent an affirmative indication to the contrary in the governing statute or rule. Neither Federal Rule of Evidence 410 nor Federal Rule of Criminal Procedure 11(e)(6) contains an anti-waiver provision or otherwise demonstrates congressional or rulemaking intent to bar defendants from agreeing to impeachment use of plea-discussion statements. Consequently, a defendant may knowingly and voluntarily waive these protections and permit impeachment use of such statements.
Yes. A defendant may waive the protections of Rule 410 and Rule 11(e)(6). A prosecutor may use plea-discussion statements to impeach a testifying defendant who offers testimony inconsistent with those statements, if the defendant entered a knowing and voluntary waiver allowing such use.
Text and structure: The Court began with a general presumption that statutory and rule-based protections that exist for an individual litigant's benefit are waivable unless the law clearly says otherwise. Rule 410 and Rule 11(e)(6) bar admission of plea-related statements against a defendant, subject to two enumerated exceptions (fairness/completeness and perjury prosecutions), but neither textually forbids waiver. The Court rejected the negative-inference argument that listing two exceptions implies all others are prohibited, reasoning that explicit anti-waiver language would be the ordinary way to disallow waiver. Precedent and policy: The Court analogized to the routine enforceability of waivers in criminal practice (e.g., plea waivers, waivers of constitutional trial rights) and to the use of otherwise excluded statements for impeachment (e.g., Harris v. New York allowing impeachment with statements obtained in violation of Miranda). The impeachment-only use here was viewed as a limited, truth-promoting application that deters perjury without authorizing the government to introduce the statements affirmatively in its case-in-chief. Plea bargaining dynamics: The Court rejected claims that permitting waiver would chill plea discussions. To the contrary, it found that allowing parties to negotiate waivers can facilitate more proffer sessions by addressing prosecutorial concerns about defendants abusing the process by testifying inconsistently at trial. Enforcing voluntary waivers aligns with longstanding respect for negotiated agreements in criminal cases. Limits and concurrences: Concurring opinions emphasized the narrowness of the holding—limited to impeachment use based on the waiver at issue—and cautioned against assuming broader admissibility (e.g., use in the case-in-chief) absent clear agreement or further guidance. The dissent argued that the rules were intended to encourage frank plea discussions and that permitting waivers undermines that goal by shifting leverage to the government and inviting incremental erosion of the rules' protections. The majority, however, found no textual or structural basis to override the background presumption of waivability and upheld the district court's admission for impeachment.
Mezzanatto is foundational to modern federal proffer practice. After this decision, prosecutors routinely require "Mezzanatto waivers" in proffer letters, at minimum permitting impeachment use if the defendant later testifies inconsistently. The case reframes Rule 410/Rule 11 protections as personal, waivable rights rather than categorical exclusions, thereby altering defense strategy when counseling clients about cooperation. While Mezzanatto expressly addresses impeachment use, many courts have grappled with the scope of waivers and, in some jurisdictions, have enforced broader clauses permitting rebuttal or even case-in-chief use if clearly agreed to. For law students, the case illustrates how evidentiary rules interact with bargaining dynamics, the doctrine of waiver, and the tension between truth-seeking and policy-based exclusions.
United States v. Mezzanatto reshaped the landscape of plea negotiations and evidentiary exclusions by recognizing that defendants may waive Rule 410 and Rule 11 protections to permit impeachment use of proffer statements. The decision aligns with a broader doctrinal pattern of enforcing voluntary waivers of litigation rights and privileges, while carefully confining the specific holding to impeachment based on the agreement before the Court. For practitioners and students, Mezzanatto underscores that evidentiary rules interact dynamically with bargaining. The enforceability and scope of a waiver turn on clear drafting and informed consent. Its legacy is the ubiquitous "Mezzanatto clause" in federal proffer agreements and the enduring need to balance cooperation incentives with the risks that waiver-driven admissibility can pose at trial.