Cal. Gov. Code § 11507

At any time before the matter is submitted for decision, the agency may file, or permit the filing of, an amended or supplemental accusation or District Statement of Reduction in Force. All parties shall be notified of the filing. If the amended or supplemental accusation or District Statement of Reduction in Force presents new charges, the agency shall afford the respondent a reasonable opportunity to prepare his or her defense to the new charges, but he or she shall not be entitled to file a further pleading unless the agency in its discretion so orders. Any new charges shall be deemed controverted, and any objections to the amended or supplemental accusation or District Statement of Reduction in Force may be made orally and shall be noted in the record.