Answer
Perjury, under Article 183 of the Revised Penal Code (as amended by Republic Act No. 11594), is the willful and deliberate assertion of a falsehood under oath upon a material matter. Its four elements are: (1) the accused made a statement under oath or executed an affidavit upon a material matter; (2) the statement was made before a competent officer authorized to receive and administer oaths; (3) in that statement the accused made a willful and deliberate assertion of a falsehood; and (4) the sworn statement is required by law or made for a legal purpose.
Willfulness is essential — the declarant must have intentionally asserted a falsehood knowing it to be false; a mere mistake, an honest opinion, or a legal conclusion does not amount to perjury. The falsehood must also concern a material matter, one that is significant to the issue or proceeding in which the statement is made.