Perjury is the act of lying or making false statements while under oath, usually during a legal proceeding like a trial or deposition. When someone swears to tell the truth but deliberately provides false information, they are committing perjury. This is considered a serious crime because it undermines the integrity of the legal system and can lead to wrongful convictions or unjust outcomes. The consequences of perjury can be severe, including fines and imprisonment. Courts rely on truthful testimony from witnesses to make fair decisions, so when someone lies, it can damage the trust in the judicial process. Ensuring honesty in legal matters is crucial for justice to prevail.