I've never seen any officials behind the line actually do anything, they are a complete waste of time because, like the referee, they would have to base a decision on a split-second view of something they might not have a perfect view of anyway. I think AL and RK are absolutely right that more technology is the only answer. Every other major sport uses technology to one degree or another, so football, having got under way with goal line cameras, will undoubtedly begin to see the benefits of a variety of measures. The problem will be finding a way to implement them without interrupting the flow of the game unnecessarily, and RK's suggestion of giving teams a limited number of appeals would help with this.