Which model rule restricts lawyers from representing new clients in matters related to former clients?

Model Rule 1.9 specifically addresses the duties lawyers have regarding the representation of former clients. This rule prohibits lawyers from representing new clients in matters that are substantially related to the former client’s case if it would create a conflict of interest. The rationale behind this rule is to protect the confidentiality of information obtained during the prior representation and to maintain the integrity of the attorney-client relationship.

When a lawyer takes on a new client in a matter that is closely tied to past representations, there is a risk that they may inadvertently use or disclose confidential information learned from the former client. The rule helps to ensure that a lawyer does not take advantage of the trust and confidences shared by a former client.

In contrast, the other options pertain to different aspects of ethical practice and do not specifically restrict representation based on a prior client relationship. For instance, Model Rule 1.1 focuses on competence in representation, Model Rule 1.4 deals with communication with clients, and Model Rule 1.3 emphasizes diligence in representing clients. These rules, while crucial to legal practice, do not address the specific concern of conflicts arising from representing new clients in relation to past clients.