45 CFR §681.26

1. (a)The ALJ conducts a hearing in order to determine whether a defendant is liable for a civil penalty, assessment, or both and, if so, the appropriate amount of the penalty and/or assessment. The hearing will be recorded and transcribed, and the transcript of testimony, exhibits admitted at the hearing, and all papers filed in the proceeding constitute the record for a decision by the ALJ.
2. (b)NSF must prove a defendant's liability and any aggravating factors by a preponderance of the evidence.
3. (c)A defendant must prove any affirmative defenses and any mitigating factors by a preponderance of the evidence.