Public records must be kept for their entire retention period regardless of whether the device is county property or state property or personal property.
Two provisions of Georgia law make clear that all records, even those created with non-county devices or instantiated in some atypical physical form, must be retained as the state's law requires.
First, O.C.G.A. 50-18-99 (c): "All records created or received in the performance of a public duty or paid for by public funds by a governing body are deemed to be public property and shall constitute a record of public acts."
Second, O.C.G.A. 50-18-91 (5): ""Records" means all documents, papers, letters, maps, books (except books in formally organized libraries), microfilm, magnetic tape, or other material, regardless of physical form or characteristics, made or received pursuant to law or ordinance or in performance of functions by any agency."
As for federal law, if an election record involves at least one federal contest, then that record--be it an email, a text-message, an instant messaging chat log, an Excel spreadsheet, or what have you--might someday end up in the hands of a receiving federal agency, such as the Department of Justice or the National Archives and Records Administration (NARA), so the federal definition of record applies in that regard.
44 U.S.C. 3301 defines records as "all recorded information, regardless of form or characteristics, made or received by a Federal agency under Federal law or in connection with the transaction of public business" ... NARA glosses that as follows: "For practical purposes, Federal records are recorded information regardless of format, created or received in the process of conducting Government activities" and so on.
Specific to the personal devices issue, January 2023 NARA guidance lays it out: "Electronic messages created or received in the course of agency business are likely federal records. This includes electronic messages sent or received on personal devices that meet the definition of a record."
This webpage created by Douglas Lucas on Wednesday, 16 August 2023. Last edited Tuesday, 16 November 2023. Serves as a footnote for my article TBD.