Service of due process is a privilege set forth by the Constitution. All citizens of the United States hold the right to be informed of being summoned. A process server handles the tasks such as serving legal documents, filing court papers and retrieving court documents. Their main job is to serve legal documents to a defendant after which they must have actual evidence that the papers were served. The proof of service must be notarized and given to the individual who required the papers to be served.
Process servers are legally required to serve papers according to the law of their state. Process serving laws may differ from state to state. The main reason process serving is necessary is to ensure that the due process of law is upheld in the United States.
If papers aren't served properly the court may not be able to rule on a case that the individual was not legally made aware of the case. If the service is deemed to be improper than the entire case may be thrown out.