42 CFR § 423.658 - Conduct of hearing.
(a) The hearing is open to the parties and to the public.
(b) The hearing officer inquires fully into all the matters at issue and receives in evidence the testimony of witnesses and any documents that are relevant and material.
(c) The hearing officer provides the parties an opportunity to enter any objection to the inclusion of any document.
(d) The Part D sponsor bears the burden of going forward and must first present evidence and argument before CMS presents its evidence and argument.