What is attorney-client privilege and what is its impact on the law?

"The attorney-client privilege ... authorizes a client to refuse to disclose, and prevent others from disclosing, confidential communications between lawyer and client, [and] is considered a hallmark of our jurisprudence." (People v. Navarro (2006) 138 Cal.App.4th 146, 156; see Evid. Code, 954.) "The privilege is fundamental to our legal system and furthers the public policy of ensuring every person's right to freely and fully confer with and confide in his or her lawyer in order to receive adequate advice and a proper defense." (People v. Navarro, supra, at p. 156.) An attorney is obligated to claim the attorney-client privilege whenever privileged communication is sought to be disclosed. (Evid. Code, 955.)