Process service expert witnesses may opine regarding the process server’s work product. The National Association of Professional Process Servers writes on unsworn declarations and affidavits of service:
Unsworn Declarations Made Under Penalty of Perjury An Unsworn Declaration made under Penalty of Perjury is a written or printed recitation by the process server of the facts and circumstances surrounding the delivery of legal process to a particular person or entity consistent with applicable state or federal court rule or law. The declaration is to be signed only by the person making the statement.
Affidavits of Service An “affidavit” is a written or printed declaration or statement of facts made voluntarily, confirmed by the oath or affirmation of the party making it, and taken before an officer having the authority to administer such oath. An “affidavit of service” is intended to certify the service of a writ, notice or other legal document.