Final answer:
Lawyers have an ethical obligation to use information relating to the representation of a client only in ways that do not harm the client, guided by standards set in landmark cases and professional conduct codes. They are prohibited from using such information to a client's disadvantage unless exceptional circumstances apply and informed consent is obtained.
Step-by-step explanation:
Lawyers are bound by ethical standards to ensure they act in the best interest of their clients. According to rule standards similar to those set forth in cases like Glasser v. United States and Padilla v. Kentucky, a lawyer must not use information that could disadvantage their client unless specific exceptional circumstances apply. The Sixth Amendment's Assistance of Counsel Clause is critically important here, as it has been interpreted to mean that a lawyer must avoid conflicts of interest that could harm their client's representation. Moreover, professional conduct guidelines prohibit attorneys from using information to the detriment of a client, safeguarding the client's interests and legal rights, which include the right to an attorney, the right to remain silent, and the right to be informed that anything one says can be used against them in court.
The landmark case Strickland v. Washington sets the standard for what constitutes effective legal representation, requiring that counsel's performance be measured against an objective standard of reasonableness. In the instance that information related to client representation might be used to an existing client's disadvantage, the lawyer must typically obtain informed consent from the client after full disclosure of the situation. Failure to adhere to these principles can result in professional disciplinary action and potentially harm the client's case or legal standing.