49 CFR 5.71: Separation of functions.

For those OAs or OST components whose regulations provide for a separation of decisional personnel from adversarial personnel in an administrative enforcement proceeding, any agency personnel who have taken an active part in investigating, prosecuting, or advocating in the enforcement action should not serve as a decision maker and should not advise or assist the decision maker in that same or a related case. In such proceedings, the agency's adversarial personnel should not furnish ex parte advice or factual materials to decisional personnel. When and as necessary, agency employees involved in enforcement actions should consult legal counsel and applicable regulations and ethical standards for further guidance on these requirements.