The attorney-client privilege is a rule that preserves the confidentiality of communications between lawyers and clients. Under that rule, attorneys may not divulge their clients' secrets, nor may others force them to. The purpose of the privilege is to encourage clients to openly share information with their lawyers and to let lawyers provide effective representation.
Generally, the attorney-client privilege applies when:
Lawyers may not reveal oral or written communications with clients that clients reasonably expect to remain private. A lawyer who has received a client's confidences cannot repeat them to anyone outside the legal team without the client's consent. In that sense, the privilege is the client's, not the lawyer's—the client can decide to forfeit (or waive) the privilege, but the lawyer cannot.
The privilege generally stays in effect even after the attorney-client relationship ends, and even after the client dies. In other words, the lawyer can never divulge the client's secrets without the client's permission, unless some kind of exception (see below) applies. (United States v. White, 970 F.2d 328 (7th Cir. 1992); Swidler & Berlin v. United States, 524 U.S. 399 (1998).)
The attorney-client privilege is, strictly speaking, a rule of evidence. It prevents lawyers from testifying about, and from being forced to testify about, their clients' statements. Independent of that privilege, lawyers also owe their clients a duty of confidentiality. The duty of confidentiality prevents lawyers from even informally discussing information related to their clients' cases with others. They must keep private almost all information related to representation of the client, even if that information didn't come from the client.
Lawyer-client communications are covered by the attorney-client privilege only if the circumstances lend themselves to confidentiality. For example, clients who speak to their lawyers about pending lawsuits in private, with no one else present, can reasonably expect secrecy. If someone were to surreptitiously record the conversation, that recording would probably be inadmissible in court.
But a client who speaks to a lawyer in public wouldn't be able to prevent someone who overheard the conversation from testifying about it. Similarly, a client can forfeit the attorney-client privilege by repeating a conversation with an attorney to someone else, or by having a third person present during a conversation with the lawyer. No matter who hears or learns about a communication, however, the lawyer typically remains obligated not to repeat it.
Preliminary communications between a potential client and a lawyer are normally subject to the attorney-client privilege. That means that lawyers can't disclose what prospective clients reveal in confidence even if the lawyers never ends up representing them. (In re Auclair, 961 F.2d 65 (5th Cir. 1992).) To be sure, though, you should confirm with a prospective lawyer that the privilege applies before you reveal anything you want to keep secret.
Discussions of previous acts are generally subject to the attorney-client privilege. If, for example, if a client tells his lawyer that he robbed a bank or lied about assets during a divorce, the lawyer probably can't disclose the information.
But if a client initiates a communication with a lawyer for the purpose of committing a crime or an act of fraud in the future, the attorney-client privilege typically doesn't apply. Likewise, most states allow—or require—attorneys to disclose information learned from a client that will prevent death or serious injury. Many have a similar rule where revealing otherwise confidential information would prevent or remedy financial injury due to a crime or fraud.
The attorney-client privilege differs somewhat from state to state, and between state and federal court. When speaking to an attorney about a legal matter, make sure to go over the scope of the attorney-client privilege and the duty of confidentiality. The lawyer should be able to explain the specific law that applies to your situation, including relevant legal rules not mentioned in this article.