A state marshal may, on any special occasion, depute, in writing on the back of the process, any proper person to serve it. After serving the process, such person shall make oath before a justice of the peace that he or she faithfully served the process according to such person’s endorsement thereon and did not fill out the process or direct any person to fill it out; and, if such justice of the peace certifies on the process that such justice of the peace administered such oath, the service shall be valid.