Final answer:
A criminal defense attorney may not disclose confidential information without consent, refuse representation based on discrimination, or fail to advocate vigorously for a client's rights irrespective of personal beliefs in the defendant's guilt. They also must maintain client confidentiality in public discussions.
Step-by-step explanation:
The question pertains to the ethical obligations and limitations of a criminal defense attorney in the United States regarding special protections provided to defendants. In instances of serious crimes, a criminal defense attorney may not: A) Refuse to represent a defendant based on their race, ethnicity, or other protected characteristics, due to anti-discrimination laws. B) Disclose confidential information shared by the client without the client's consent, as this would violate attorney-client privilege. C) An attorney should still advocate for their client's rights and present a vigorous defense, regardless of personal belief in the defendant's guilt, as per the ethical requirement to provide zealous representation. D) The attorney cannot publicly discuss case details in a way that violates the client's privacy, respecting the confidentiality required by the attorney-client relationship. These principles are derived from the Sixth Amendment, which guarantees the right to legal counsel and a fair trial inclusive of effective assistance of counsel. Key cases such as Gideon v. Wainwright extended the right to counsel to all defendants who cannot afford an attorney, ensuring the fundamental fairness of the criminal justice process.