Can a judge who is a defendant in a civil matter refuse to testify as a witness or witness?

[68 Cal.App.3d 96] The commission argues that the privilege not to be called as a witness and not to testify may be asserted only by a Defendant in a criminal case, and that all other persons, including a judge who is the subject of a proceeding under article VI, section 18, must appear when subpoenaed as a witness but may assert the privilege to refuse to disclose any matter that may tend to incriminate them, as provided in Evidence Code section 940 and People v. Whelchel (1967) 255 Cal.App.2d 455, 456, 63 Cal.Rptr. 258).