The registered owner of the vehicle cited in a Violation Notice shall have the opportunity for a hearing in which said owner may contest the merits of the alleged violation. The lessee of a vehicle cited in a Violation Notice likewise shall be afforded the opportunity for a hearing of the same kind afforded the registered owner. The formal or technical rules of evidence shall not apply at any such hearing. Such hearings shall be recorded, and the person conducting the hearing on behalf of the Administrator shall be empowered to administer oaths and to secure by subpoena both the attendance and testimony of witnesses and the production of relevant books and papers. Persons appearing at such a hearing may be represented by counsel at their own expense.