How Do I Maintain Privilege During an Internal Investigation?

Introduction

Internal investigations are one of the most powerful tools companies have to detect, address, and remediate potential misconduct. But they also come with legal risks—especially when it comes to protecting privileged communications.

If an internal investigation isn’t carefully structured, your notes, interviews, emails, and findings could all become discoverable in litigation or enforcement proceedings. That means what you thought was confidential may one day become part of the public record.

So how do you preserve the attorney-client privilege and work product protection during an internal investigation?

This post explains what privilege is, how it applies in corporate investigations, and practical steps to help you maintain it.

What Is Privilege—and Why It Matters

There are two key legal doctrines that can protect internal investigation materials from disclosure:

1. Attorney-Client Privilege

Protects confidential communications between a lawyer and their client made for the purpose of seeking or providing legal advice.

2. Work Product Doctrine

Protects documents and materials prepared in anticipation of litigation, including investigative notes, legal strategies, and attorney impressions.

To keep investigation materials protected, you need to meet the legal criteria for privilege—and take steps to preserve it throughout the process.

When Does Privilege Attach in an Internal Investigation?

Privilege doesn’t automatically apply just because lawyers are involved.

To invoke the attorney-client privilege, you generally need to show:

• The communication was between a lawyer and a client (or the client’s agent)

• It was made in confidence

• It was made for the purpose of giving or receiving legal advice

Work product protection applies to documents created in anticipation of litigation—not just as part of general risk management or HR practices.

Practical Steps to Maintain Privilege During an Internal Investigation

1. Clearly Define the Purpose of the Investigation

From the outset, make clear that the investigation is being conducted at the direction of counsel and for the purpose of providing legal advice to the company. Use engagement letters, investigation charters, or internal memos to formally document this.

2. Involve Legal Counsel Early—and Directly

Whether in-house or external, legal counsel should:

• Be involved from the start

• Direct the scope, methods, and documentation of the investigation

• Communicate with witnesses and internal stakeholders on behalf of the company

If HR or Compliance is running the investigation with minimal legal input, courts may find privilege does not apply.

3. Use “Upjohn Warnings” During Interviews

When company counsel interviews employees, it’s critical to clarify:

• The lawyer represents the company, not the individual

• The conversation is privileged and confidential

• The company controls the privilege

• The company may choose to waive privilege later

This type of disclaimer is called an Upjohn warning and is essential to preserve privilege. The so-called Upjohn warning takes its name from the seminal Supreme Court case Upjohn Co. v. United States, in which the Court held that communications between company counsel and employees of the company are privileged, but the privilege is owned by the company and not the individual employee.

4. Mark Documents Clearly

Documents created as part of the investigation—interview notes, memos, communications—should be labeled appropriately:

• “Privileged and Confidential: Attorney-Client Communication”

• “Prepared at the Direction of Counsel”

• “Attorney Work Product”

This helps establish your intent and strengthens your privilege claims.

5. Limit Distribution

The more people who see privileged material, the more risk of waiving privilege.

• Share documents only with those who need to know

• Avoid forwarding privileged content in broader email chains

• Train stakeholders on privilege basics to prevent accidental waiver

6. Consider Separate Reports

If you expect to share findings externally, consider preparing:

• A full, privileged internal report

• A separate, non-privileged summary or presentation

This allows transparency without sacrificing legal protection.

When Might Privilege Be Lost or Waived?

Privilege can be lost if:

• You voluntarily disclose privileged materials to third parties

• You use legal advice as a defense in litigation

• You fail to maintain confidentiality

• Counsel is not clearly involved or tied to legal advice

You can’t assume privilege will apply—protect it deliberately.

Final Thoughts

Privilege is a powerful protection—but it’s fragile.

If you’re running or overseeing an internal investigation, treat privilege as a deliberate legal strategy. Involve counsel early, define the purpose clearly, and take consistent steps to protect confidentiality.

Because once privilege is lost, you can’t get it back—and the consequences could be significant.