Whether it's one's home town hero, or the quarterback for the other team -- you know it when you see it -- because it's obvious. By that, I mean "intentional grounding".
When a QB drops back to pass and finds himself "under pressure", about to be sacked for a loss, perhaps even for a safety in his own end zone, at times they'll just throw the ball where nobody can possibly catch it, sometimes even into the stands. It's no big secret. We all know they do that to have the "pass" ruled incomplete, so they can trot back up to the original line of scrimmage and get on with the next play, their team having not suffered the loss of yardage that would have happened if they were sacked. It happens all the time, both in professional and college football.
And that's just wrong.
The "experts" will tell you there are a couple different reasons for QBs getting away with such shenanigans.
First, they might say he was outside the "tackle box", and therefore no penalty is warranted. That begs a question. Just where is this tackle box? And does anybody know exactly what the boundaries are? There certainly aren't any lines on the field to define it. Yours truly would further respond by saying, "Tackle box? The whole damn FIELD is a tackle box. HELLO? By that logic, should linebackers only be allowed to take down a running back between the hash marks? Wide receivers aren't allowed to run INSIDE the same hash marks? What's the difference? ANYBODY HOME?"
Or they might say the QB managed to throw the ball past the line of scrimmage. Near as I can tell, it's an incomplete pass if the ball sails into Row 5, as long as when it was airborne the ball went "out of bounds" a yard PAST the original line of scrimmage. But it just might be intentional grounding if the same ball went out of bounds a yard BEHIND the same line of scrimmage. How stupid is THAT?
Besides, every pro QB, and most of those in college, can flip the ball 50 yards off their back foot anytime they feel like it. Heaving it past the line of scrimmage is hardly a problem, even though there might not be a receiver nor defender within 20 yards of where the ball sailed out of bounds.
So forget the tackle box, the line of scrimmage, and all the other excuses, and just call it like it is. I know it, you know it, the players and coaches know it, and anybody else watching a game knows it. The only people that don't seem to understand it is the people making the rules in the NFL. It's not the refs' fault. Though they likely don't quite understand them either, they're bound by those very rules, but I suspect they privately look upon them with the same disdain as I do.
When a QB is under pressure and throws the ball away without the remotest chance of it ever being caught -- in my book, that's intentional grounding, and should be called as such.