According to Illinois Legal Aid, an alias summons is a second summons that is issued if the person being sued did not receive the first summons. A second name or alias is often included on the new court document.
The Office of the Clerk of the Circuit Court of Cook County in Illinois indicates that a summons expires 30 days after it has been filed. In order to move the case forward, the individual bringing suit must file an alias summons. The local sheriff's office has the authority to serve the new document. It is also legal to send the summons through certified mail.