What are the requirements for a supplemental brief in a criminal case?

review the record and determine whether there are any arguable issues on appeal. (People v. Wende, supra, 25 Cal.3d 436.) Defendant was advised by counsel of his right to file a supplemental brief within 30 days from the date the opening brief was filed.

Defendant filed a supplemental brief raising several issues. Most of defendant's challenges relate to events occurring before his plea in 2018, which are both untimely and unappealable without a certificate of probable cause, which he did not obtain. (Cal. Rules of Court, rules 8.304(b), 8.308(a); 1237.5; People v. Panizzon (1996) 13 Cal.4th 68, 74-78.)