I) Applicable Rules of Professional Conduct

A. RULE 4.4: RESPECT FOR RIGHTS OF THIRD PERSONS

…(b) A lawyer who receives a document relating to the representation of the lawyer's client and knows or reasonably should know that the document was inadvertently sent shall promptly notify the sender.

Comment

…[2] Paragraph (b) recognizes that lawyers sometimes receive documents that were mistakenly sent or produced by opposing parties or their lawyers. If a lawyer knows or reasonably should know that such a document was sent inadvertently, then this Rule requires the lawyer to promptly notify the sender in order to permit that person to take protective measures. Whether the lawyer is required to take additional steps, such as returning the original document, is a matter of law beyond the scope of these Rules, as is the question of whether the privileged status of a document has been waived. Similarly, this Rule does not address the legal duties of a lawyer who receives a document that the lawyer knows or reasonably should know may have been wrongfully obtained by the sending person. For purposes of this Rule, "document" includes e-mail or other electronic modes of transmission subject to being read or put into readable form.

[3] Some lawyers may choose to return a document unread, for example, when the lawyer learns before receiving the document that it was inadvertently sent to the wrong address. Where a lawyer is not required by applicable law to do so, the decision to voluntarily return such a document is a matter of professional judgment ordinarily reserved to the lawyer. See Rules 1.2 and 1.4.

2) Excerpts from the Comment to Rule 1.6

…Acting Competently to Preserve Confidentiality

[16] A lawyer must act competently to safeguard information relating to the representation of a client against inadvertent or unauthorized disclosure by the lawyer or other persons who are participating in the representation of the client or who are subject to the lawyer's supervision. See Rules 1.1, 5.1 and 5.3.

[17] When transmitting a communication that includes information relating to the representation of a client, the lawyer must take reasonable precautions to prevent the information from coming into the hands of unintended recipients. This duty, however, does not require that the lawyer use special security measures if the method of communication affords a reasonable expectation of privacy. Special circumstances, however, may warrant special precautions. Factors to be considered in determining the reasonableness of the lawyer's expectation of confidentiality include the sensitivity of the information and the extent to which the privacy of the communication is protected by law or by a confidentiality agreement. A client may require the lawyer to implement special security measures not required by this Rule or may give informed consent to the use of a means of communication that would otherwise be prohibited by this Rule.

See also the following selected annotations to RULE 4.4 RESPECT FOR RIGHTS OF THIRD PERSONS from ABA, Annotated Model Rules of Professional Conduct 5th Ed. (2003).

II. State Bar ethics opinions. Where available, links to the full text are attached.

Alaska Opinion 97-1 (1/17/97)

Arizona Opinion 93-14 (9/23/93)

Colorado Opinion 102 (3/21/98)

Connecticut Opinion 96-4 (3/14/96)

District of Columbia Opinion 318 (12/02)

District of Columbia Opinion 256 (5/16/95)

Illinois Opinion 98-4 (1/99)

Kentucky Opinion E-374 Revised (11/95)

Maine Opinion 146 (12/9/94)

Maryland Opinion 00-04 (2/16/00)

Massachusetts Opinion 94-6 (3/22/94)

Massachusetts Opinion 99-4 (7/15/99)

Michigan Opinion RI-179 (11/16/93)

New York State Opinion 749 (12/14/01) Confidentiality; E-mail; Internet

New York State Opinion 700 (5/7/98)

North Dakota Opinion 95-14 (12/4/95)

Ohio Supreme Court Ethics Committee Opinion 93-11 (12/3/93)

Oregon Opinion 1998-150 (4/98)

Pennsylvania Opinion 99-150 (11/18/99)

Philadelphia Opinion 94-3 (6/94)

Utah Opinion 99-01 (1/29/99)

Virginia Opinion 1702 (11/24/97)

III. Articles on Metadata

Board of Governors of the State Bar of Florida state that it is unethical to mine hidden data from e-texts. The full text from the Florida Bar News is available here.

Hricik, The Transmission and Receipt of Invisible Confidential Material Information, 15 NO. 1 Professional Lawyer 18 (2004)

Anthony Davis, "The Intersection of Professional Responsibility and Technology", New York Law Journal, Mar. 7, 2005.

Sylanski, Threat of Metadata and malpractice Initiates Problems for Attorneys, 3 NO. 15 Lawyers J. 8 (2001