It's a good point, McTavish, and I do apologise for underestimating the educational value of this thread (as well as the tongue-in-cheek language, which I see hasn't come across so well). Maybe I can backtrack/change tack and start afresh?
"From behind and over his head..."
You're right that this simple phrase is deceptively complex in interpretation. How to tackle it? How about miming to yourself the various possibilities of throw-in and then asking, "was that from behind and over my head?" If so, go with that. It seems to me there aren't really that many legal options.
Anything that isn't delivered "from behind" isn't legal. Anything that doesn't go "over" isn't legal. And the use of the word "and" in "behind
and over" seems to imply one continuous action.
Would the waist high throw satisfy the requirements? Or the Aussies rules 'bounce throw'? I think so, if done skilfully and in one smooth action. But the chances of a player doing this in a game are pretty slim, so not something I'll be losing any sleep over. Cross that bridge in the unlikely event I come to it.
This is from the USSF "Advice to referees on the Laws of the Game":
15.3 PROPERLY TAKEN THROW-IN
Law 15 states that the thrower “delivers the ball from behind and over his head.” This phrase does not mean that the ball must leave the hands from an overhead position. A natural throwing movement starting from behind and over the head will usually result in the ball leaving the hands when they are in front of the vertical plane of the body. The throwing movement must be continued to the point of release. A throw-in directed straight downward (often referred to as a “spike”) has traditionally been regarded as not correctly performed; if, in the opinion of the referee such a throw-in was incorrectly performed, the restart should be awarded to the opposing team. There is no requirement in Law 15 prohibiting spin or rotational movement. Referees must judge the correctness of the throw-in solely on the basis of Law 15.
So they say no to the 'spike throw', though seemingly purely on the basis of tradition. And, confusingly, by offering the possibility that a referee could judge "such a throw-in incorrectly performed", they imply that this type of throw could also be "correctly performed".
Go figure.
Personally, my only question when the inevitable shouts for "foul throw, ref!" cry out is, "was it from behind and then over the head, and in one fluid motion?" When I say, "I know it when I see it" what I mean is, having asked that question, I know when the answer is "no".
Does that clear things up?