5 CFR 185.132: The hearing and burden of proof.

(a) Where requested in accordance with § 185.109 the ALJ shall conduct a hearing on the record in order to determine whether the defendant is liable for a civil penalty or assessment under § 185.103 and, if so, the appropriate amount of any such civil penalty or assessment considering any aggravating or mitigating factors.

(b) The authority shall prove defendant's liability and any aggravating factors by a preponderance of the evidence.

(c) The defendant shall prove any affirmative defenses and any mitigating factors by a preponderance of the evidence.

(d) The hearing shall be open to the public unless otherwise closed by the ALJ for good cause shown.