29 CFR § 417.9 - Evidence; contumacious or disorderly conduct.
(a) Formal rules of evidence or procedure in use in courts of law or equity shall not obtain. Rules of evidence are to be within the discretion of the Administrative Law Judge. However, it shall be the policy to exclude testimony or matter which is irrelevant, immaterial, or unduly repetitious.
(b) Contumacious or disorderly conduct at a hearing may be ground for exclusion therefrom. The refusal of a witness at any hearing to answer any questions which have been ruled to be proper shall, in the discretion of the Administrative Law Judge be ground for striking all testimony previously given by such witness on related matter.
(c) At any stage of the hearing the Administrative Law Judge may call for further evidence or testimony on any matter. After the hearing has been closed, no further information shall be received on any matter, except where provision shall have been made for it at the hearing, or except as the Administrative Law Judge or Director may direct by reopening the hearing.