What is the burden of establishing prejudicial error in dismissing a writ petition?

Appellants have the burden of affirmatively establishing the trial court committed prejudicial error. (Denham v. Superior Court (1970) 2 Cal.3d 557, 564.) An aspect of carrying this burden is submitting an appellant's opening brief with appropriate references to the record. (Cal. Rules of Court, rule 8.204(a)(1)(C).) Although plaintiff's opening brief contends the trial court erred because the record shows he served respondents, that brief does not identify who the respondents are and does not provide a citation to where in the record the proof of service is located. In the absence of a document showing the service was made in accordance with legal requirements, we must conclude plaintiff has failed to affirmatively demonstrate the trial court committed error when it dismissed his writ petition. Such a petition must be properly served "within three years after the action [wa]s commenced." ( 583.210, subd. (a).) When, as occurred in this case, proper service has not been made within the three-year period, dismissal is mandatory under section 583.250.