The defendant in a lawsuit must be served (delivered) a summons or citation (an order from the court to appear and answer the lawsuit) and a copy of the lawsuit (1) to provide due process (fairness) by giving the defendant notice of the lawsuit and the opportunity to appear in court and defend the lawsuit; and (2) to give the court personal jurisdiction (authority) over the defendant.

In Louisiana, the process of serving a defendant with a summons or citation, along with a copy of the lawsuit, is a critical step in the legal process. This procedure ensures due process by notifying the defendant of the lawsuit and allowing them the chance to appear in court to defend themselves. Additionally, it establishes the court's personal jurisdiction over the defendant. Louisiana law requires that service of process be carried out in a manner prescribed by the Louisiana Code of Civil Procedure. Typically, this involves personal delivery to the defendant, but if that is not possible, the law provides for alternative methods such as service by mail, service by publication, or service through the Secretary of State if the defendant is not a resident or is evading service. The service must be executed by a person authorized by law, such as a sheriff or a professional process server. Failure to properly serve a defendant can result in delays or dismissals of the lawsuit, emphasizing the importance of adhering to the specific requirements set forth by Louisiana statutes and rules.