When dealing with an attorney, the attorney-client privilege is what keeps communication between the two private. This is important in promoting openness and honesty, and is sometimes considered the most important privilege.

 In order for this concept to apply, several things must hold. First, the person with the privilege must be an actual client communicating with a member of the court who is performing the role of an attorney. Outsiders may not be present, and the communication must be to obtain legal advice, legal services, or some other legal proceeding. The client must claim this privilege, and they should be sure that it has not been waived. The privilege usually still holds upon the client's death, unless it is believed that revoking it would better serve the client's interests, such as in disputes among heirs.

This privilege only protects the communication between the client and the attorney, not the information that is disclosed. If the client shares the information with an additional third party, the communication here is not protected simply because the information shared is the same as the protected communication with the attorney. In fact, this may be grounds for waiving the privilege. The privilege also does not hold if the communication is being used to further commit a crime, so attorneys may also be allowed to share information if they believe that doing this may stop the crime.

Whether or not the privilege is granted also depends on the court. Certain states do not allow for it. For example, in Washington state, only the communications from the client to the attorney are protected, not the other way around. On the other hand, an attorney in California has his or her communications protected. Therefore, it is important to know your state's law regarding the attorney-client privilege. Federal courts must decide whether to use the state's law or common law in determining whether or not to apply the rule. State law is usually chosen in cases where there is a dispute between parties of different states or who are non-U.S. citizens, and common law is usually used for cases involving the violation of a federal law.

Because communication between an attorney and their client is vital for a fair case, the attorney-client privilege is important in promoting an open atmosphere. With it, the attorney can hopefully have enough information to perform his or her duties the best they can.