(a) All civil process and papers of the District Court shall be served by the constables of the respective districts, except that the administrative judge of a particular district may order the papers and process served by the sheriff of the county.

(b) All criminal and traffic process, including warrants and summonses for witnesses, shall be served by the constables of the respective districts, or by the sheriffs of the respective counties or by State or local police as the administrative judge of the district shall direct. However, summonses to witnesses in these cases may be served by mail, rather than by personal service, if the administrative judge of the district directs.