5 C.F.R. § 2422.27
How does the FLRA address determinative challenged ballots and objections?
(a) Investigation. The FLRA investigates objections and/or determinative challenged ballots that are sufficient in number to affect the results of the election.
(b) Burden of proof. An objecting party bears the burden of proof on objections by a preponderance of the evidence. However, no party bears the burden of proof on challenged ballots.
(c) FLRA action. After investigation, the FLRA takes appropriate action consistent with § 2422.30.