Final answer:
A lawyer must not represent a client adverse to a prospective client if there is a conflict of interest, as this violates attorney-client privilege and ethical standards set by legal precedence, ensuring the right to effective legal representation under the Sixth Amendment is protected.
Step-by-step explanation:
A lawyer who has obtained information from a prospective client must not represent a client adverse to the prospective client if such representation creates a conflict of interest with potential for damage to the interests of one or more clients. This ethical mandate is rooted in the fundamental principles of attorney-client privilege and confidentiality. When a lawyer receives confidential information from a prospective client, using that information or acting against the interests of that prospective client in a subsequent representation could result in prejudiced legal actions and is thus impermissible.
Notable cases such as Glasser v. United States affirm the necessity for conflict-free counsel as protected under the Assistance of Counsel Clause of the Sixth Amendment. Furthermore, the standards set forth in cases like Strickland v. Washington emphasize that attorneys have the duty to perform competently, highlighting the importance of avoiding such conflicts to ensure effective counsel. Additionally, principles from Padilla v. Kentucky detail that defense attorneys also have specific responsibilities regarding advising clients on matters such as deportation.
Overall, the prohibition is designed to maintain the integrity of the legal process, uphold the confidential and trust-based nature of lawyer-client relationships, and ensure that the right to an attorney and an impactful defense is preserved.