Hi Deagian:
TDA Rule 37, adopted at the 2013 Summit applies here:
37: Verbal Declarations / Acting in Turn
A: Players must act in turn. Verbal betting declarations in turn are binding. Chips put in the pot in turn stay in the pot. An undercall (betting less than the current call amount) is a mandatory full call if made facing an opening bet multi-way on any betting round, or facing any bet heads up. In all other situations, TD’s discretion applies. For purposes of this rule, in blind games the posted BB is the opening bet on the first round.
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You need to first decide whether this action was in response to the opening bet or some intervening bet. I take by your description that this is pre-flop, and the blinds have been posted THEN Player A pushes out 30,000?
In that case Player C is not responding to the opening bet (the BB), but rather an intervening bet. So it's going to be up to TD discretion in this case.
The way the rule is intended, IMO is deliberately skewed in favor of ruling a full call (or a full raise in this case), unless there is some compelling and understandable reason why Player C would have gotten the action wrong. Remember that the new TDA Rule 2 clearly states it is player's responsibility to follow the action.
But the rule is left to your discretion given all the circumstances in the situation, because he wasn't responding to the opening bet.
IF on the other hand, this were post-flop and A were first to open a betting round for 30,000, and C just was inattentive and tough he'd opened for the BB, according to Rule 37 he would definitely be responsible for a full raise.
Thanks for the great case.