In the front or back? What if the player is side on? Not trying to be funny, I just think there are practical limitations.Why can't they have GPS trackers in players vests?
Personally I think tonight's decision was correct, I just don't understand what took so long. As soon as you get the picture with the line you can see his leg is offside and from there it's a black and white decision. I'm not a fan of VAR for more subjective decisions as that often creates more controversy.