An observer is defined in the Rules of Golf as one who is appointed by the Committee to assist a referee to decide questions of fact and to report to him any breach of a Rule. Before play, it is important for a referee to reach an understanding with his observer as to their respective duties. Usually it is best for the observer to work ahead of the match as much as possible. The referee should stay close to the players at all times and be readily available to answer questions.
An observer, by stationing himself in the area where the ball may be expected to come to rest, may be in a position to determine questions of fact that the referee, from his position near the players, could not hope to decide. For example, it is always useful to know before going forward whether a player’s ball is out of bounds or where it last crossed the margin of a water hazard. Only a Rules official can properly determine this. Similarly, it is important to know whether a ball was still in motion when deflected or stopped by an outside agency (such as a spectator) and, if so, whether the deflection was deliberate or whether the ball had come to rest and was moved by an outside agency. If it was moved when at rest, the observer may know the spot from which it was moved.
When players are in difficulty on opposite sides of the hole it is desirable for the observer to station himself by one of the balls if possible, so that play of each ball can be observed. Preferably, he should watch the ball to be played first, so that he may have the opportunity to resume his normal position ahead of play.
When there is a large crowd, an observer can perform other duties by placing himself ahead of the play. To help ensure fair play, it is a duty of a referee to guard against any possible interference by spectators. An observer can be of great assistance by moving spectators away from places where a ball may go, asking spectators to be alert before shots are played to the green and in guarding a ball that may have gone into the crowd. Very often an observer is in a better position than the referee to work with the marshals to obtain proper control of the crowd. In a match or grouping with large galleries, the services of an alert observer are invaluable to a referee.