What is a defensive 3 second violation?

Defensive 3-second violation is a basketball rule that prohibits defenders from remaining in the key area for more than three seconds without actively guarding an offensive player. The key area is the painted rectangular area that extends from the baseline to the free throw line. If a defensive player were to violate this rule and remain in the key area for more than three seconds, the referee would blow the whistle to signal a defensive 3-second violation, resulting in a technical foul being awarded to the opposing team. This penalty is assessed regardless of whether the offensive team has possession of the ball or is attempting a field goal. The purpose of this rule is to prevent defenders from camping in the key area, which could lead to congestion and hinder the flow of the game.