Perjury

the act of lying under oath in court.

Perjury is knowingly lying under oath.

Perjury is knowingly lying under oath. If a person believes he is telling the truth, but is factually incorrect, he’s neither a liar nor perjurer. If he knowingly and intentionally makes factually incorrect statements under oath, he is both a liar and perjurer. If the statement is not made under oath, he is merely a liar.
Clients often comment that opposing counsel is a "liar" or "perjurer." If opposing counsel makes a factually incorrect statement, it doesn’t necessarily mean he is lying. Who knows what he believes, or what his client told him? Try to stay calm when this happens. See Courtroom Etiquette. Perjury may run rampant in divorce trials. Criminal prosecution for perjury in a civil cases is virtually non-existent. One Massachusetts Family Court judge sent cases to the district attorney ( who failed to prosecute). No one likes being lied to, especially judges. The "jerk" factor often decides cases. Which party is the bigger jerk? Judges are human. They often like one side more than the other. Point out your spouse’s perjury at trial, and he’ll assume "jerk" status.