The ruling on the field is down by contact.
An official shall declare the ball dead and the down ended when a runner is contacted by an opponent and touches the ground with any part of his body other than his hands or feet. The ball is dead the instant the runner touches the ground. A runner touching the ground with his hands or feet while in the grasp of an opponent may continue to advance; or if, after contact by an opponent, any part of a runner’s leg above the ankle or any part of his arm above the wrist touches the ground, the runner is down.
The ruling on the field is incomplete.
A player who makes a catch may advance the ball. A forward pass is complete (by the offense) or intercepted (by the defense) in the field of play, at the sideline, or in the end zone if a player, who is inbounds:
a) secures control of the ball in his hands or arms prior to the ball touching the ground; and
b) touches the ground inbounds with both feet or with any part of his body other than his hands; and
c) after (a) and (b) have been fulfilled, performs any act common to the game (e.g., tuck the ball away, extend it forward, take an additional step, turn upfield, or avoid or ward off an opponent), or he maintains control of the ball long enough to do so.
The ruling on the field is down at the 1-yard line.
(2) If a defensive player, in the field of play, intercepts a pass or catches or recovers a fumble, backward pass, scrimmage kick, free kick, or fair catch kick, and his original momentum carries him into his end zone where the ball is declared dead in his team’s possession. The ball belongs to the defensive team at the spot where the player’s foot or other body part touched the ground to establish possession. If that spot is in the end zone, the result of the play is a touchback, even if the ball is not on, above, or beyond the goal line. (11-6-1)