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 (the complaint) (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 Connecticut, the process of serving a defendant with a summons and complaint is governed by state statutes and rules of civil procedure. The service of process is essential to ensure due process, which means that the defendant is given proper notice of the lawsuit and the chance to appear in court to defend against the claims. Additionally, service of process gives the court personal jurisdiction over the defendant, which is the court's authority to make decisions affecting the defendant's rights. The Connecticut Practice Book outlines specific procedures for serving individuals, businesses, and government entities within the state. Service can be made by a state marshal, proper officer, or an indifferent person. The rules require that the summons and complaint be delivered in a manner that is reasonably calculated to inform the defendant of the action, which can include personal delivery, delivery to someone at the defendant's residence, or by certified mail, among other methods. Failure to properly serve a defendant can result in the dismissal of the lawsuit or the inability to enforce a judgment.