(a) In representing a client, an attorney shall not use means that have no substantial purpose other than to embarrass, delay, or burden a third person, or use methods of obtaining evidence that violate the legal rights of such a person.

(b) An attorney who receives a document, electronically stored information, or other property relating to the representation of the attorney's client and knows or reasonably should know that the document, electronically stored information, or other property was inadvertently sent shall promptly notify the sender.

(c) In communicating with third persons, an attorney representing a client in a matter shall not seek information relating to the matter that the attorney knows or reasonably should know is protected from disclosure by statute or by an established evidentiary privilege, unless the protection has been waived. An attorney who receives information that is protected from disclosure shall (1) terminate the communication immediately and (2) give notice of the disclosure to the person entitled to enforce the protection against disclosure. If the person entitled to enforce the protection against disclosure is represented by an attorney, the notice required by this Rule shall be given to the person's attorney.

[1] Responsibility to a client requires an attorney to subordinate the interests of others to those of the client, but that responsibility does not imply that an attorney may disregard the rights of third persons. It is impractical to catalogue all such rights, but they include legal restrictions on methods of obtaining evidence from third persons and unwarranted intrusions into privileged relationships, such as the client-attorney relationship.

[2] Section (b) recognizes that attorneys sometimes receive a document, electronically stored information, or other property that was inadvertently sent or produced by opposing parties or their attorneys. A document, electronically stored information, or other property is inadvertently sent when it is accidentally transmitted, such as when an email or letter is misaddressed or a document, electronically stored information, or other property is accidentally included with information that was intentionally transmitted. If an attorney knows or reasonably should know that such a document, electronically stored information, or other property was sent inadvertently, this Rule requires the attorney promptly to notify the sender in order to permit that person to take protective measures. Whether the attorney is required to take additional steps, such as returning the document, electronically stored information, or other property, is a matter of law beyond the scope of these Rules, as is the question of whether the privileged status of a document, electronically stored information, or other property has been waived. Similarly, this Rule does not address the legal duties of an attorney who receives a document, electronically stored information, or other property that the attorney knows or reasonably should know may have been inappropriately obtained by the sending person. For purposes of this Rule, “document, electronically stored information, or other property” includes, in addition to paper documents, email and other forms of electronically stored information, including embedded data(commonly referred to as “metadata”), that is subject to being read or put into readable form. Metadata in electronic documents creates an obligation under this Rule only if the receiving attorney knows or reasonably should know that the metadata was inadvertently sent to the receiving attorney.

[3] Some attorneys may choose to return a document or delete electronically stored information unread, for example, when the attorney learns before receiving it that it was inadvertently sent. Where an attorney is not required by applicable law to do so, the decision to voluntarily return such a document or delete electronically stored information is a matter of professional judgment ordinarily reserved to the attorney. See Rules 19-301.2 and 19-301.4.

[4] Third persons may possess information that is confidential to another person under an evidentiary privilege or under a law providing specific confidentiality protection, such as trademark, copyright, or patent law. For example, present or former organizational employees or agents may have information that is protected as a privileged attorney-client communication or as work product. An attorney may not knowingly seek to obtain confidential information from a person who the attorney knows or reasonably should know has no authority to waive the privilege. Regarding current employees of a represented organization, see also Rule 19-304.2 (4.2).

Model Rules Comparison--Sections (a) and (b) of Rule 19-304.4 are substantially similar to the language of Model Rule 4.4 of the Ethics 2000 amendments to the ABA Model Rules of Professional Conduct. Section (c) substantially restores to the Rule Maryland language as it existed prior to a 2017 amendment, with slight modification.