A person upon whom this chapter confers a privilege against disclosure of the confidential matter or communication waives the privilege if the person or his or her predecessor, while holder of the privilege, voluntarily discloses or consents to disclosure of any significant part of the matter or communication. This section does not apply if the disclosure is itself a privileged communication.
Wis. Stat. § 905.11
Testimony of an accomplice who waived her privilege is admissible even though she had not been tried or granted immunity. State v. Wells, 51 Wis. 2d 477, 187 N.W.2d 328 (1971). A litigant's request to see his or her file that is in the possession of current or former counsel does not waive the attorney-client and work-product privileges and does not allow other parties to the litigation discovery of those files. Borgwardt v. Redlin, 196 Wis. 2d 342, 538 N.W.2d 581 (Ct. App. 1995), 94-2701. A lawyer's voluntary production of documents in response to opposing counsel's discovery request does not constitute a waiver of the attorney-client privilege under this section when the lawyer does not recognize that the documents are subject to the attorney-client privilege and the documents are produced without the consent or knowledge of the client. The agency doctrine does not apply to waiver of attorney-client privilege as it relates to privileged documents. Harold Sampson Trust v. Linda Gale Sampson Trust, 2004 WI 57, 271 Wis. 2d 610, 679 N.W.2d 794, 02-1515. The controlling principle of waiver is the privilege holder's voluntary disclosure of any significant part of the matter or communication. It is clear from the terms of this section that a matter or communication can have several "significant parts." The significance of any portion of a communication is measured by the importance of its subject matter to the overall communication. State v. Schmidt, 2016 WI App 45, 370 Wis. 2d 139, 884 N.W.2d 510, 15-0457.