Written by David Boyer, Partner. Last updated October 1, 2026.

Joint Defense Agreement: Protecting Privilege in Federal Criminal Investigations

On This Page

• Why Joint Defense Agreements Matter in Federal Cases
• What a Joint Defense Agreement Is and What It Is Not
• How the Common-Interest Doctrine Works Under Federal Law
• Conflict of Interest and Withdrawal Risks
• Steps to Take Before Joining or Drafting a Joint Defense Agreement
• How Evergreen Attorneys Can Help With Joint Defense Agreements
• Frequently Asked Questions

Federal prosecutors routinely investigate multiple people and entities at once. When the government issues a federal target letter or a federal grand jury subpoena to several subjects, each person’s defense lawyer may hold pieces of a larger picture. A joint defense agreement allows those separately represented parties to share privileged information and coordinate strategy without waiving the protections that keep their communications confidential. Handled correctly, a joint defense agreement strengthens every participant’s position. Handled poorly, or entered without careful analysis, it can expose confidences, create disqualifying conflicts, and hand prosecutors evidence they would not otherwise possess.

Why Joint Defense Agreements Matter in Federal Cases

Federal investigations, particularly in federal white collar criminal defense matters, often target overlapping conduct by business partners, executives, employees, and corporate entities. Each participant typically retains separate counsel. Without a framework for sharing information, each defense team operates in isolation, unable to compare the government’s evidence, identify weaknesses in the prosecution’s theory, or coordinate a consistent factual presentation.

A joint defense agreement addresses that problem by establishing ground rules under which participants and their lawyers can exchange otherwise privileged communications. The stakes are significant: if a court later finds that sharing information outside the attorney-client relationship waived the privilege, the government can compel disclosure of those communications. That outcome can turn a defensible case into an indefensible one.

What a Joint Defense Agreement Is and What It Is Not

A joint defense agreement is a written arrangement among separately represented parties who share a common legal interest in a federal investigation or criminal case. It permits participants and their lawyers to coordinate defense strategy and share privileged information without creating a new attorney-client relationship between a participant and another participant’s lawyer.

What a joint defense agreement does not do is equally important. It does not create an independent privilege. As the Department of Justice has explained in its guidance on joint defense agreements and common-interest privilege, the protection is generally an extension of existing attorney-client privilege or work-product protection, not a standalone right. A communication shared under a joint defense agreement must independently qualify for privilege, relate to the common legal interest, further the joint defense effort, and remain confidential. Communications that fall outside those boundaries, including those that involve the crime-fraud exception or information obtained independently, are not protected merely because a joint defense agreement exists.

The Second Circuit described this principle in United States v. Schwimmer, 892 F.2d 237, 243 (2d Cir. 1989), explaining that the joint defense privilege, more properly called the common-interest rule, protects confidential communications made during a joint defense effort undertaken by parties and their counsel. The Ninth Circuit similarly recognized in United States v. Gonzalez, 669 F.3d 974 (9th Cir. 2012), that the doctrine extends the attorney-client privilege and can apply in both civil and criminal matters involving actual or potential litigation.

How the Common-Interest Doctrine Works Under Federal Law

Federal Rule of Evidence 501 directs federal courts to apply federal common law when determining privilege claims, unless the Constitution, a federal statute, or Supreme Court rules provide otherwise. Federal Rule of Evidence 502 addresses limitations on waiver, including situations where privileged information is disclosed to a third party. Together, these rules form the framework that courts use to evaluate whether a joint defense agreement preserved or waived privilege.

To invoke the common-interest doctrine successfully, a participant generally must show:

• The communication was otherwise protected by attorney-client privilege or work-product doctrine.
• The participants shared a common legal interest at the time of the communication.
• The communication was made to further the joint defense effort.
• The participants maintained confidentiality and did not disclose the communication outside the group.

Courts apply these requirements strictly. An oral understanding may offer some protection, but written agreements are far more reliable because they document the scope of the common interest, the participants, and the confidentiality obligations. Circuit courts vary in how they define “common legal interest” and evaluate the sufficiency of a joint defense arrangement, so the governing circuit’s standards must be analyzed before any information is exchanged.

What a Written Joint Defense Agreement Should Address

A carefully drafted written agreement should cover the following provisions:

• Identity of all participants and their counsel
• The precise common legal interest that connects the parties
• What types of information may be shared and the permitted methods of communication
• Confidentiality obligations that survive withdrawal or termination
• Procedures for withdrawal and the effect of withdrawal on previously shared information
• Restrictions on use of shared information if a participant later cooperates with the government or becomes adverse to another participant

Conflict of Interest and Withdrawal Risks

Conflicts are the most dangerous practical risk in any joint defense arrangement. At the outset of a federal investigation, participants may appear to share the same interest: resisting the government’s theory. As the investigation develops, interests can diverge sharply. One participant may receive a cooperation offer. Another may learn that a co-participant’s conduct, rather than shared conduct, is the primary government target. A corporate entity may decide to cooperate for reduced penalties, placing individual employees at greater risk.

When these conflicts emerge, a participant’s lawyer may face a disqualifying conflict that forces withdrawal. If privileged information has already been shared under a joint defense agreement, the withdrawing participant’s new counsel inherits a complicated situation: the former joint defense members know what the withdrawing participant disclosed, and the withdrawing participant knows what others disclosed. The agreement’s terms on continued confidentiality, use restrictions, and cooperation become critical.

DOJ policy states that a corporation’s participation in a joint defense agreement does not by itself make the corporation ineligible for cooperation credit, and prosecutors may not request that a corporation refrain from entering into such agreements. This means the government cannot penalize a company simply for joining a joint defense group, but it also means a participant may leave the agreement and cooperate at any time, subject to the agreement’s terms on use of shared information.

Defense counsel should evaluate potential conflicts before any confidential information is exchanged, not after.

Steps to Take Before Joining or Drafting a Joint Defense Agreement

1. Retain separate federal defense counsel before discussing the proposed agreement with any other participant or participant’s lawyer.
2. Identify every proposed participant and evaluate whether your legal interests are genuinely aligned or merely appear aligned at the current stage of the investigation.
3. Assess potential future conflicts, including the possibility that one participant may cooperate, face different charges, or become a government witness.
4. Insist on a written agreement that specifies the common legal interest, permitted communications, confidentiality obligations, withdrawal procedures, and restrictions on use of shared information.
5. Review the governing circuit’s standards for the common-interest doctrine to confirm that the proposed agreement meets those requirements.
6. Do not share any privileged information until the agreement is signed and your counsel has confirmed that the communication qualifies for protection.
7. Reevaluate the agreement periodically as the investigation develops, particularly after any participant receives a target letter, cooperation offer, or superseding indictment.

How Evergreen Attorneys Can Help With Joint Defense Agreements

Evergreen Attorneys represents individuals, executives, and entities facing federal criminal investigations and corporate federal investigations where joint defense agreements are a core component of white collar criminal defense strategy. Partners Zachary Newland and David Boyer have extensive experience with federal investigations and prosecutions, and advise clients on the formation, scope, and risks of joint defense arrangements throughout the investigation and pretrial process.

The firm evaluates proposed joint defense agreements for privilege sufficiency under the governing circuit’s law, identifies conflict risks before information is exchanged, drafts and negotiates agreement terms that protect clients if interests later diverge, and coordinates with co-defense counsel to build a cohesive defense while preserving each client’s independent options. Evergreen Attorneys serves federal criminal defense clients nationwide, including matters in Colorado federal courts and across all federal districts.

 

Frequently Asked Questions

What is a joint defense agreement?

A joint defense agreement is an arrangement among separately represented people or entities who share a common legal interest in a federal investigation or criminal case. It allows participants and their lawyers to coordinate strategy and share otherwise privileged information without waiving applicable attorney-client or work-product protection. The agreement does not make every communication automatically confidential; its scope depends on the facts, governing law, and its terms.

Does a joint defense agreement protect attorney-client communications?

A joint defense agreement generally preserves the confidentiality of communications that were already eligible for attorney-client or work-product protection and were shared to advance a common legal interest. Federal Rule of Evidence 501 directs federal courts to apply federal common law to privilege claims, while Rule 502 addresses limitations on waiver. A joint defense agreement is not a guarantee that every conversation among participants is privileged, particularly if no lawyer is involved, the communication falls outside the common defense, or confidentiality is compromised.

What should someone consider before joining a joint defense agreement during a federal criminal investigation?

Before joining, a person should understand the identity of every participant, the precise common legal interest, what information may be shared, how the group will communicate, and what happens if interests diverge. The agreement should address withdrawal, continued confidentiality, future cooperation with the government, use of information in later adverse proceedings, and whether it creates any attorney-client relationship with another participant’s lawyer. Separate counsel should evaluate conflicts before confidential information is exchanged.

Can a joint defense agreement prevent a participant from cooperating with the government?

A joint defense agreement does not automatically prevent a participant from cooperating with the government, but it may restrict the participant from disclosing protected information learned from other members. DOJ policy states that a corporation’s participation in a joint defense agreement does not by itself make the corporation ineligible for cooperation credit. The agreement should expressly address cooperation, withdrawal, and the permitted use of information if a participant later becomes adverse or assists prosecutors.

When should a federal defense lawyer review a joint defense agreement?

A federal defense lawyer should review a proposed joint defense agreement before a person signs it or shares confidential information with another subject, witness, codefendant, or another person’s lawyer. Early review is especially important after a target letter, grand jury subpoena, agent contact, search, or any indication that several people may face related federal charges. Evaluation of the proposed scope, privilege risks, conflicts, and withdrawal provisions should occur as early as possible in the defense process.

If you are facing a federal investigation involving multiple subjects and need to evaluate or negotiate a joint defense agreement, contact Evergreen Attorneys at (303) 948-1489 for a confidential case evaluation.