Although each case can be different and different states have different rules, the general rule in federal court is that a party will not have waived the privilege if the disclosure was inadvertent, the party took reasonable steps to avoid disclosure, and the party promptly tries to correct the error.
What do we mean by privilege?
In both civil and criminal cases, certain types of documents and communications are privileged. Privileged means that that the information does not have to be shared with the adversary in a civil case or with the government in a criminal case. The opposing party cannot ask about the privileged information or use it as evidence against the party asserting the privilege.
Two major types of privileged information are attorney-client communications, where a client seeks or receives legal advice from his counsel, and attorney-work product. Attorney work product is material an attorney creates when he or she anticipates litigation.
The privilege can be waived
But what happens if an attorney accidentally or inadvertently discloses this information? The concern is that the privilege might be waived, that is, by disclosing the information the material is no longer privileged and may be used against the party in court.
Different states have different rules and every situation might be different but Federal Rule of Evidence 502 provides a good starting point. According to Rule 502, if a party inadvertently discloses information, it will not be considered a waiver of the privilege if the party took reasonable steps to prevent the disclosure and promptly attempts to rectify the error. In a civil case a party that accidentally discloses privileged information can seek its return pursuant to Federal Rule of Civil Procedure 26.
On the other hand, it a party intentionally discloses information that might otherwise be privileged, the disclosure will waive the privilege.