Service of process refers to the legal notice required for a person to be subject to criminal or civil sanctions. Service of process is required in most countries before a court can obtain jurisdiction over an individual. The exact rules for what constitutes appropriate service differ depending on the jurisdiction and the country.
In order for a court to adjudicate a dispute and impose penalties or mandate action, the court must have jurisdiction over the individual. Jurisdiction is obtained, in part, by issuing proper service of process. Under the constitutional laws protecting due process in the United States, and equivalent rules and stipulations in many other countries, a person has a right to appropriate legal process, which involves being made aware of a legal action and having the opportunity to speak on his own behalf.
When a plaintiff files a lawsuit or a prosecutor obtains an indictment against an individual, the court cannot simply make a ruling without giving the person a chance to speak up for himself. The individual must know that the court action has been instituted. The function of service of process, and the related rules associated with service of process, is to make sure the person knows of the action and has the chance to speak.
In most common law jurisdictions, such as the United States, Canada, England, and Australia, rules stipulate that notice of the legal action, or "process," must be served by a qualified individual. Usually, the rules mandate that such an individual be an adult, a court official, and not a party to the litigation. In other words, the plaintiff cannot serve process on the defendant, and process is usually served by a sheriff or some other officer of the court.
In civil law jurisdictions, such as France, a special official called a huissier de justice is entrusted with the responsibility of issuing formal service of process. This person can deliver the service of process physically in person. He could also deliver the service through some type of certified mail.
Most jurisdictions allow substitute service if a person cannot easily be found. For example, if someone's address is unknown or the person is in hiding, it may be difficult to serve him with notice. A legal notice of the action printed in the newspaper for a set number of weeks is often sufficient to count as service, and the court can then hold a hearing and issue a default judgment against the defendant if he does not show up.