The start of a hand?

[EWillers]

I think the most critical aspect of this for cash games is concerning disputes about a hand.

A common rule is that any dispute about a hand must be stated before the start of the next hand. I think a move towards defining when a hand begins as when the first card is in the air is in order.

The circumstances have changed. Many rooms (especially concerning cash games, tourneys to a lesser extent) now employ shuffle machines. There is no longer a "first riffle". To apply the "first riffle" rule would mean that a hand would start when the dealer pushes the green button? I guess? The point is, I don't see a good bright line like the first riffle when using a shuffle machine.

The bright line could be the delivery of the first card to the small blind. Many rooms use that as a cutoff point for straddling, adding on, and things of this nature.