When is a change of possession awarded, and how do I rule on a ball touched in flight?

Change of possession occurs when:

• the sixth touch is made;
• the ball is dropped or passed and goes to ground (the mark is where it first hits the ground);
• a player mishandles the ball and it is accidentally knocked forward into any other player;
• the half is touched while in possession, at the point of the touch (in-goal, the nearest point on the seven metre line);
• the ball in the half's control contacts the ground in the in-goal area (rollball at the nearest point on the seven metre line);
• the rollball procedure is broken (at the point of the infringement);
• a player in possession steps on or outside the sideline, or the loose ball hits it, before a touch (rollball seven metres in-field).

Ball touched in flight by a defender:

• Deliberate contact, ball goes to ground: attacking team keeps the ball and the touch count restarts at zero.
• Deliberate contact, ball retrieved by an attacker without touching the ground: play continues and the next touch is zero touch.
• Deliberate contact propelling it forward and an attacker drops it while trying to regain it: attacking team keeps possession, count restarts at zero.
• Deliberate contact propelling it towards the defenders' dead ball line and an attacker drops it: change of possession.
• Unintentional contact, ball goes to ground: change of possession. If an attacker retrieves it, play and the count continue.

If the referee causes an obstruction (including the ball hitting the referee), play pauses and restarts with a rollball at the mark with the touch count unchanged.

Source: FIT Playing Rules 5th Edition, rules 9, 10.7, 12, 13 and 16.6.