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 California, the process of serving a defendant with a summons and a copy of the lawsuit is a critical step in the legal process, as it ensures due process and establishes the court's personal jurisdiction over the defendant. Due process requires that the defendant is given proper notice of the lawsuit and the opportunity to appear in court to defend against the claims. This is accomplished by delivering the legal documents in a manner prescribed by law, which may include personal service, service by mail followed by an acknowledgment of receipt, or, in some cases, service by publication if the defendant cannot be located. The California Code of Civil Procedure outlines the specific rules and methods for service of process. Failure to properly serve a defendant can result in delays or dismissal of the lawsuit, as the court may not have the authority to proceed without proof that the defendant was appropriately notified.