California Code, Penal Code - PEN § 118

(a) Every person who, having taken an oath that he or she will testify, declare, depose, or certify truly before any competent tribunal, officer, or person, in any of the cases in which the oath may by law of the State of California be administered, willfully and contrary to the oath, states as true any material matter which he or she knows to be false, and every person who testifies, declares, deposes, or certifies under penalty of perjury in any of the cases in which the testimony, declarations, depositions, or certification is permitted by law of the State of California under penalty of perjury and willfully states as true any material matter which he or she knows to be false, is guilty of perjury.

This subdivision is applicable whether the statement, or the testimony, declaration, deposition, or certification is made or subscribed within or without the State of California.

(b) No person shall be convicted of perjury where proof of falsity rests solely upon contradiction by testimony of a single person other than the defendant. Proof of falsity may be established by direct or indirect evidence.