What is the burden of proof against a proponent of nondisclosure?

"The burden of proof is on the proponent of nondisclosure, who must demonstrate a 'clear overbalance' on the side of confidentiality." (City of San Jose v. Superior Court, supra, 74 Cal.App.4th at p. 1018.) "[I]n determining whether public records which are not expressly exempted from disclosure must be disclosed over the government's objection, California courts apply the section 6255 balancing test for the catchall exception on a case-by-case basis. Where the public interest in disclosure of the records is not outweighed by the public interest in nondisclosure, courts will direct the government to disclose the requested information." (Ibid.)