ABA Model Rule of Professional Conduct 1.9(a) addresses conflicts between current clients and former clients of a lawyer. It reads: (a) A lawyer who has formerly represented a client in a matter shall not thereafter represent another person in the same or a substantially related matter in which that person’s interests are materially adverse to the interests of the former client unless the former client gives informed consent, confirmed in writing. (Emphasis added).  

Model Rule 1.18 addresses prospective clients and its paragraph (c) similarly requires analysis when a lawyer subsequently represents another person with “interests materially adverse to those of the prospective client.” Rule 1.18(c) provides: (c) A lawyer subject to paragraph (b) shall not represent a client with interests materially adverse to those of a prospective client in the same or a substantially related matter if the lawyer received information from the prospective client that could be significantly harmful to that person in the matter, except as provided in paragraph (d). If a lawyer is disqualified from representation under this paragraph, no lawyer in a firm with which that lawyer is associated may knowingly undertake or continue representation in such a matter, except as provided in paragraph (d). (Emphasis added).  

ABA Formal Opinion 497, issued February 10, 2021, titled “Conflicts Involving Materially Adverse Interests” addresses how to construe the language “interests

[that] are materially adverse to the interests of the former client” in Rule 1.9(a) and similar language used in Rule 1.18(c). It concludes:  

“Material adverseness” under Rule 1.9(a) and Rule 1.18(c) exists where a lawyer is negotiating or litigating against a former or prospective client or attacking the work done for the former client on behalf of a current client in the same or a substantially related matter. It also exists in many but not all instances, where a lawyer is cross-examining a former or prospective client. 

Material adverseness” may exist when the former client is not a party or a witness in the current matter if the former client can identify some specific material legal, financial, or other identifiable concrete detriment that would be caused by the current representation.  

However, neither generalized financial harm nor a claimed detriment that is not accompanied by demonstrable and material harm or risk of such harm to the former or prospective client’s interests suffices. 

With this guidance, attorneys addressing conflict issues related to current or former clients now have more guidance from which to address these situations.  

More information regarding this new Model Rule may be located here: 

ABA issues new guidance on definition of ‘material adverseness’ in client representation (americanbar.org) 

aba-formal-opinion-497.pdf (americanbar.org)