Legal Question in Appeals and Writs in California

Acting on it one month later might be too late. You can try to file a declaration with a very good explanation of your failure with the Court of Appeals, and ask for leave to file your brief late.

It is not clear whether you filed a petition for a writ of mandate with the Superior Court, the Appellate Division of the Superior Court, the Court of Appeal, or the California Supreme Court. (Or even Federal court.)

Unlike Mr. Cohen's answer, you actually need to file a motion to set aside the dismissal. They are governed by different rules and statutes. For example, in the Court of Appeal, motions for relief from dismissal are governed by California Rules of Court, rule 8.60 subd. (d). "For good cause, a reviewing court may relieve a party from default for any failure to comply with these rules except the failure to file a timely notice of appeal or a timely statement of reasonable grounds in support of a certificate of probable cause."

That motion would need to include the declaration, setting forth reasonable grounds for your failure to file an opening brief.

You need to have the entire matter reviewed by an appellate attorney. It matters what the writ of mandate was for, who the respondent would be (a court or a public entity) and many other factors. You may be able to just file another writ of mandate or the motion to set aside the dismissal. On the other hand you may be better off just proceeding with an appeal. Good Luck, Pat McCrary