Attorney-Client privilege is the oldest legally recognized privilege, first recognized under English Common Law in the 16th century, its antecedents go back to Roman Law.  Attorney-Client privilege derives from the classical concept of “honor.” It serves to prevent an attorney from working against the interests of his or her client. In modern terms, the privilege ensures “that one who seeks advice or aid from a lawyer should be completely free of any fear that his secrets will be uncovered.”
The purpose is to afford criminal defendants and civil litigants “sound legal advice [and] advocacy.” Privilege requires the attorney to “satisfy all of their professional responsibilities, uphold their duties of good faith and loyalty to the client, and [contribute] to the efficient administration of justice.” Privilege also protects the client from a compulsion to testify communication with their lawyer concerning the reasons for which they seek legal services.
At its core, Attorney-Client Privilege is an evidentiary rule. It prevents a lawyer from testifying, willingly or unwillingly, about client statements. The privilege belongs to the client – which means that the client can waive it, but the lawyer cannot.
The privilege attaches when one shares information with a lawyer, acting in a professional capacity (e.g., not just a “friend”), to seek legal advice or services with the intent that the communication remains private or confidential. Privilege not only applies to practicing attorneys. It also applies to lawyers not admitted to the jurisdiction, disbarred attorneys, student legal interns, and other persons who may not actually be lawyers. It also applies to the subordinates of a lawyer such a legal secretary, intern, paralegal, and so on. The lawyer need not actually take the case.
The lawyer may not share privileged information with obvious parties like prosecutors, or opposing parties, but it also with employers, friends, or even family members. Even if a client confesses guilt or liability or even dies, privilege still applies. The privilege continues even after the attorney-client relationship ends, the client’s death does NOT terminate the privilege. A lawyer can never reveal a client’s secrets without the client’s permission (barring a recognized exception.)
Privileged communications must be made under circumstances conducive to confidentiality, like in a lawyer’s office with no one else present. Jailhouse conversations with one’s lawyer in a private room where no one speaks loudly enough to be overheard by corrections officers or other inmates are confidential. Secret recordings of such communication are probably inadmissible. Parents sitting with their minor child in a meeting with the child’s lawyer, probably will not destroy the privilege. Communications made in a public place where others are likely to overhear would be less likely to create privilege. Even speaking in front of others in a lawyer’s office may constitute a waiver of privilege.
Jailhouse phone conversations are a different matter. If a prisoner is warned that phone calls may be monitored, the privilege may not attach at all. If the prison authorities monitor a phone call where a prisoner makes a damaging statement to their lawyer, or if another prisoner overhears (or even eavesdrops) then the privilege is probably waived.
A client waives privilege by repeating the information to someone else, posting it online, or by having a third person present during any conversation with the lawyer. Even under these circumstances, however, the lawyer probably remains barred from repeating client statements.
Revelations of prior acts generally fall under the attorney-client privilege. In other words, if a criminal defendant admits their guilt to their lawyer or a civil defendant tells their lawyer that they lied about a past financial disclosure, then the lawyer must treat the statement as privileged.
The same is NOT true if a client seeks the lawyer’s services to commit a crime or fraud. Most state legal ethics rules permit (but do not necessarily require) attorneys to disclose otherwise privileged information to prevent death or serious injury. Many states permit, but again don’t necessarily require, disclosure of confidential information to prevent or remedy grave financial injury arising from future crimes or frauds.
Related to, but separate from, the Attorney-Client Privilege is the attorney’s Duty of Confidentiality. The attorney-client privilege prevents lawyers from testifying in court or anywhere else about their clients’ statements. The duty of confidentiality, in contrast, applies to informal disclosures related to their clients’ cases. A lawyer must keep their clients’ secrets – which applies to almost all information related to client representation, even where the information came from sources other than the client.
What Privilege Does Not Cover
In addition to communications regarding future crimes or frauds, or public statements, or circumstances where privilege was waived, there are several things to which privilege does not apply.
The mere existence of the attorney-client relationship is not privileged. The fact that one sought legal advice or services or that one made a privileged communication is not itself subject to privilege.
On a related note, the identity of a client is not itself subject to privilege. There are a few narrow exceptions to this general rule. An exception might exist if a strong probability exists that disclosing the client’s identity implicates the client in the very criminal allegation for which legal services are sought to defend against.
A client’s identity may also be privileged if disclosure would reveal the nature of the legal problem for which services were sought or other personal, confidential information about the client. Such circumstances are rare, however, and generally, the client’s identity is not privileged.
The circumstances or purpose for which a client seeks legal services or for which the client retained an attorney, and a general description of the type of service provided are not usually privileged.
In other words, the circumstances surrounding the communication, the date on which client consulted the attorney, is not privileged. Additionally, the fact that communication occurred, or when it occurred or who participated in the communication are all not privileged either – but are probably covered by confidentiality.
An attorney’s impression of a client’s mental state, especially where the attorney is concerned about the risk that defendant would become violent, is not covered by privilege. If an attorney does reveal an impression of the client’s mental state, they are still bound by confidentiality and privilege not to disclose any confidential communications.
Police reports or other official documents later communicated to an attorney are generally not privileged – they are considered public. Likewise, billing statements and time sheets may not be privileged unless the contents might reveal client confidences or attorney theories or strategy. In such cases, bills may be redacted to protect privileged information.
In short, the attorney-client privilege belongs to the client and permits a client to keep confidential and secret most communications between an attorney and the client secret. Privilege can be asserted in the face of a legal demand for the communications.
The attorney-client privilege exists for a potential client if: 1) the non-client seeks legal advice, 2) then the non-client reasonably relies on that advice as legal advice, and 3) the attorney does not attempt to dissuade the non-client from relying on the advice.
has an additional responsibility to treat all information relating to the
representation of a client as confidential unless the client gives informed
consent for its release, the disclosure is impliedly authorized in order to
carry out the representation or the disclosure is permitted by a recognized exception
to confidentiality. 
 Edna S. Epstein, THE ATTORNEY-CLIENT PRIVILEGE AND THE WORK-PRODUCT DOCTRINE 2 (4th ed. 2001).
 United States v. Grand Jury Investigation, 401 F. Supp. 361, 369 (W.D. Pa. 1975).
 Upjohn Co. v. United States, 449 U.S. 383, 389 (1981).
 Bufkin Alyse King, Preserving the Attorney-Client Privilege in the Corporate Environment, 53 ALA. L. REV. 621, 622 (2002) (citing Upjohn, 449 U.S. at 391 (quoting Model Code of Prof’l Responsibility EC 4-1 (1980))).
 Epstein, supra note 1, at 3.
 See e.g. In re Auclair, 961 F.2d 65 (5th Cir. 1992)
 See e.g. State v. Sucharew, 205 Ariz. 16 (Ct. App. 2003)
 Katz v. United States, 386 U.S. 954 (1967)
 Stroh v. Gen. Motors Corp., 213 A.D.2d 267 (1995); State v. Shire, 850 S.W.2d 923 (Mo. Ct. App. 1993)
 In re Grand Jury Subpoena (Roe v U.S.), 781 F2d 238, 247 (2d Cir 1986); In re Michaelson, 511 F2d 882, 888 (9th Cir 1975).
 See e.g. Hays v Wood, 25 C3d 772, 785 (1979)
 United States v Legal Servs. for New York City, 249 F3d 1077, 1081 (DC Cir 2001)
 In re Grand Jury Witness (Salas v U.S.), 695 F2d 359, 362 (9th Cir 1982)
 Togstad v. Vesely, 291 N.W.2d 686 (1980), see also Model Rules of Professional Conduct 1.6, and 1.9
 Model Rules of Professional Conduct 1.6
[…] The most recent round of politically motivated charges that this or that politician is a foreign agent or subscribes to Leninist or Hitlerian political opinions is beside the point. The issue is more significant than that. I am referring, of course, to the Attorney-Client privilege. […]