A player is playing with creatures in his/her deck. It's easy to track when he/she attacks, as his creatures have lifelink, showing a distinct life total change on paper.

His opponent has been attacking for 3 each turn, and he has been gaining 3 from lifelink each turn. (i.e, attacked from 8 to 5, attack and gain 3, (going to 8 life), attacked from 8 to 5 and so forth).

On his opponent's turn, his opponent goes to attack him from 5 to 2. He realizes that last turn, he forgot to attack; because he didn't untap his creatures. It is currently in the opponent's declare attackers step.

What would you do to fix the gamestate/life totals?

Edited Tim Hughes (April 13, 2013 10:07:10 AM)

Untapping permanents in the untap step is a turn based action that doesn't use the stack {CR 502.1}

I've had many new players who have the (bad) habit of not untaping their lands unless they want to cast a spell (so after they draw), for example.

In my opinion, those creatures are untapped, because nothing caused them to be tapped, but the player has mis-represented the game state by leaving them tapped. Fix the game state by untapping the creatures, scold your player “THIS right here is why its important to physically untap your cards when your supposed to.” And allow play to proceed.

I'm assuming that since the player forgot to attack, they didn't make a life total change.

Ah this fix works if the defending player is the one who forgot to untap last turn. If instead the attacker is the one who forgot to attack last turn, I would apply no fix. (1) The error was more than a turn ago. (2) Presumably, it fixed itself at the beginning of the current turn when the attacker untapped their creatures, but we might want to double check that since this seems to be a problem with this player.

Edited Daniel Regewitz (April 19, 2013 12:25:57 PM)