Recognizing that errors occur along a continuum, an error is material if a disinterested lawyer would conclude that it is (a) reasonably likely to harm or prejudice a client; or (b) of such a nature that it would reasonably cause a client to consider terminating the representation even in the absence of harm or prejudice.

More fully:

“A lawyer’s responsibility to communicate with a client is governed by Model Rule 1.4. Several parts of Model Rule 1.4(a) potentially apply where a lawyer may have erred in the course of a current client’s representation. For example, Model Rule 1.4(a)(1) requires a lawyer to promptly inform a client of any decision or circumstance with respect to which the client’s informed consent may be required. Model Rule 1.4(a)(2) requires a lawyer to ‘reasonably consult with the client about the means by which the client’s objectives are to be accomplished.’ Model Rule 1.4(a)(3) obligates a lawyer to ‘keep a client reasonably informed about the status of a matter.’ Model Rule 1.4(a)(4), which obliges a lawyer to promptly comply with reasonable requests for information, may be implicated if the client asks about the lawyer’s conduct or performance of the representation. In addition, Model Rule 1.4(b) requires a lawyer to ‘explain a matter to the extent reasonably necessary to permit the client to make informed decisions regarding the representation.’ More broadly, the ‘guiding principle’ undergirding Model Rule 1.4 is that ‘the lawyer should fulfill reasonable client expectations for information consistent with the duty to act in the client’s best interests, and the client’s overall requirements as to the character of representation.’ A lawyer may not withhold information from a client to serve the lawyer’s own interests or convenience.

“Determining whether and when a lawyer must inform a client of an error can sometimes be difficult because errors exist along a continuum. An error may be sufficiently serious that it creates a conflict of interest between the lawyer and the client…. Where a lawyer’s error creates a Rule 1.7(a)(2) conflict, the client needs to know this fact to make informed decisions regarding the representation, including whether to discharge the lawyer or to consent to the conflict of interest. At the other extreme, an error may be minor or easily correctable with no risk of harm or prejudice to the client….

Several state bars, including the North Carolina State Bar, have issued opinions that provide guidance to practicing attorneys.  For example: “Errors that fall between the two extremes of the spectrum must be analyzed under the duty to keep the client reasonably informed about his legal matter. If the error will result in financial loss to the client, substantial delay in achieving the client’s objectives for the representation, or material disadvantage to the client’s legal position, the error must be disclosed to the client. Similarly, if disclosure of the error is necessary for the client to make an informed decision about the representation or for the lawyer to advise the client of significant changes in strategy, timing, or direction of the representation, the lawyer may not withhold information about the error.”

The ABA does not “purport to precisely define the scope of a lawyer’s disclosure obligations.”  But believes more specific guidance should be available.

“With these considerations in mind, the Committee concludes that a lawyer must inform a current client of a material error committed by the lawyer in the representation. An error is material if a disinterested lawyer would conclude that it is (a) reasonably likely to harm or prejudice a client; or (b) of such a nature that it would reasonably cause a client to consider terminating the representation even in the absence of harm or prejudice.”

Regarding Former Clients:

“If a material error relates to a former client’s representation and the lawyer does not discover the error until after the representation has been terminated, the lawyer has no obligation under the Model Rules to inform the former client of the error…. Good business and risk management reasons may exist for lawyers to inform former clients of their material errors when they can do so in time to avoid or mitigate any potential harm or prejudice to the former client. Indeed, many lawyers would likely choose to do so for those or other individual reasons. Those are, however, personal decisions for lawyers rather than obligations imposed under the Model Rules.”

ABA Formal Opinion No. 481  (April 17, 2018).

Note that Professor Ciolino disagrees with the Committee regarding a lawyer’s duty to his or her Former Clients.  In Ciolino’s view, Rule 1.16(d) requires a lawyer to inform a former client of the lawyer’s prior material error if it is “reasonable and practicable” for the lawyer to do so.  In particular, it is “reasonable” under to require a lawyer to inform a former client about errors if doing so would “prevent, mitigate or rectify substantial injury to the financial interests or property” of the former client, and, when such disclosure is “practicable”, the Rule should require nothing less.

Dane Ciolino, “New ABA Opinion Gets it Wrong on a Lawyer’s Duty to Admit Malpractice” https://lalegalethics.org/new-aba-opinion-gets-it-wrong-on-a-lawyers-duty-to-admit-malpractice/?utm_source=Louisiana+Legal+Ethics+Newsletter&utm_campaign=084af55b09-Newsletter_May_2018&utm_medium=email&utm_term=0_08c89000b4-084af55b09-48881729 (April 30, 2018).