(a) A hearing under this part shall be conducted by the Presiding Officer on the record:

(1) To determine whether the respondent is liable under 39 U.S.C. 3018,and,to,clean.

(b) The Postal Service must prove its case against a respondent by a preponderance of the evidence.

(c) The parties may offer for insertion onto the record such relevant evidence as they deem appropriate and as would be admissible under the generally accepted rules of evidence applied in the courts of the United States in nonjury trials, subject, however, to the sound discretion of the Presiding Officer in supervising the extent and manner of presentation of such evidence. In general, admissibility will hinge on relevancy and materiality. However, relevant evidence may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice, or by considerations of undue delay, waste of time, or needless presentation of cumulative evidence.