Black and White: Public Knowledge

Joe Frankino

10/27/2016 11:00:00 AM

I've noticed there's a perception both in tournament play, and in online discussions, that once a card has been revealed by a card effect, the opponent is entitled to know the identity of that card while it's in that location. I've seen that assumption made at literally all levels of competition.

I'm not exactly sure when this practice started, but I've seen it a lot recently with the introduction of Metalfoes and their ability to easily set Spells and Traps from the deck. The justification for asking your opponent for this information, and the willingness to give it, is usually because of “Public Knowledge”. Since that term's been discussed a whole bunch, it's appropriate to talk about it here.

This week on Black and White, we go over the concept of Public Knowledge: what it means, how it impacts your games and what information you're responsible for being truthful about.

Public Knowledge (n.)
There are two places where Public Knowledge is defined. The first is in rulebook 9.1 on page 46 which says…

The number of cards in a player's hand and Decks, the cards in their Graveyards, and each player's current LP are all public knowledge and both players can verify these things at any time. If asked, you must answer these things to your opponent truthfully. You are allowed to pick up and verify the cards in your opponent's Graveyard but you must ask their permission first. Also, you may not change the order of the cards when verifying their Graveyard.

Public Knowledge is also defined in Yu-Gi-Oh! Tournament Policy. Section V. E says…

The following items are considered to be public knowledge, unless a card effect says otherwise. Duelists must answer questions involving the following topics truthfully. Failure to do so may result in a Disqualification penalty.

- The number of cards in a Duelist's hand

- The number of cards in a Duelist's Deck (this includes the Main Deck, Side Deck, and Extra Deck)

- The number and names of the cards in a Duelist's Graveyard and face-up banished cards

- Both Duelist's current Life Point totals

- Any notes taken by either Duelist during a Duel

- Information printed on a specific, named card.

And because it's referenced here, notes may only be taken for the following:

- Duelists should keep a written record of both Duelists' Life Points for each Duel.

- Tracking of mandatory effect reminders.

- Tracking of turns and turn counters.

Anything else is not considered Public Knowledge and does not need to be revealed.

Once more for those in the back: Anything not listed above as being Public Information does not need to be revealed to your opponent.

What Does That Mean?
Suppose you're playing against Burning Abyss. Your opponent Xyz Summons Beatrice, Lady of the Eternal while you have a face-down Solemn Warning. You know that if you Warning the Beatrice, your opponent will Special Summon Dante, Pilgrim of the Burning Abyss from their Extra Deck, and you want to make sure you're prepared for that, but you also don't remember exactly what Pilgrim's ATK points are.

You ask your opponent, “What's Pilgrim's attack?” Dante Pilgrim's ATK is information on a specific, named card, so it counts as Public Knowledge and the question must be answered truthfully. (If the Burning Abyss player doesn't know the answer off-hand or doesn't want to give away that they have it in their Extra Deck, they can ask for a judge's assistance and they can get the information.)

 Gold Sarcophagus
Gold Sarcophagus123505
Set Legendary Decks II
Number LDK2-ENY22
Type Spell Card
Attribute SPELL 
Rarity Common
Card Text

Banish 1 card from your Deck, face-up. During your second Standby Phase after this card's activation, add that card to your hand.

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Or, suppose you've activated Gold Sarcophagus Last Turn banishing Shiranui Solitaire. In the next turn, your opponent asks “when do you get Solitaire?” This is also considered Public Information since any turn counters are considered notes and notes are Public Knowledge. You must answer truthfully and say “in two more of my Standby Phases.”

Now, those situations seem pretty straight-forward. The following scenarios are the ones I need to address.

On their first turn, your opponent used two Metalfoes effects, setting Metalfoes Counter closest to the deck with Metalfoes Steelen's effect and a Metalfoes Combination with Metalfoes Silverd's effect. He then set two more cards to his Spell and Trap Card Zone from his hand before passing. On your turn, you're considering using Mystical Space Typhoon and you ask “which one is the Counter?” Your opponent responds “this one” and reveals the set Counter closest to the deck.

The first two examples were hypothetical, but realistic. The previous example was something that actually happened and not a “what-if” or something I made up just to prove a point. Players are actually doing this, and for the last few months, I can't figure out why. Take a look back at the actual policy and rulebook definitions of Public Knowledge. Set cards do not fall anywhere under those definitions. A revealed card is Public Knowledge only while that card is revealed. Once it's face-down, it's a face-down card and you have to remember that it's there. If a card is revealed by a card effect, it does not automatically become Public Knowledge for the remainder of the game.

Here's another example that actually happened. Over the course of a game, a Burning Abyss player has used a Scarm, Malebranche of the Burning Abyss effect to search a Farfa, Malebranche of the Burning Abyss, a The Phantom Knights of Silent Boots effect to search for a Phantom Knights' Fog Blade and a Reinforcement of the Army to search for The Phantom Knights of Ragged Gloves. The opponent asks for cards in hand, and the player rightfully responds with “four” since the number of cards in hand is listed as being Public Knowledge. The opponent then asks “which ones do I know?” and the player, for some reason, says exactly what was searched for on previous turns.

And one more example, just in case it hasn't set in yet. Player Normal Summons Majespecter Toad – Ogama to search for Majespecter Tornado and then uses a Metalfoes effect to destroy Toad and set Metalfoes Counter from the deck. He then sets two more traps from his hand, one of them being a second copy of Majespecter Tornado. On the next turn, his opponent asked which one was the Tornado and I visibly saw the hesitation in the player as he tried to recall which of the two Tornados was the one the opponent knew was there. He was very close to revealing the previously unknown Tornado and giving his opponent way more information than he had previously.

 Majespecter Raccoon - Bunbuku
Majespecter Raccoon - Bunbuku122423
Set 2016 Mega-Tins Mega Pack
Number MP16-EN126
Level 3
Type Pendulum/Effect Monster
Monster Spellcaster
Attribute WIND 
A / D 1200 / 900
Rarity Ultra Rare
Card Text

When this card is Normal or Special Summoned: You can add 1 "Majespecter" monster from your Deck to your hand. You can only use this effect of "Majespecter Raccoon - Bunbuku" once per turn. Cannot be targeted or destroyed by your opponent's card effects.

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I want to be clear on this. At the moment, there's nothing in tournament policy that's preventing you from revealing information that your opponent shouldn't be privy to. However, speaking as someone who plays this game on a competitive level, voluntarily giving your opponent the info they need to beat you is a strategically poor move. If they're not supposed to have private info about what's in your hand, don't give it to them. They need to remember what was played and where it was set if they want to play around it.

Your objective is to use your cards to win the game, and you can't do that if you also have to remember what info your opponent does and doesn't have about the cards you've used. And to reiterate that point, a card's identity previously being Public Knowledge doesn't make it Public Knowledge for the remainder of the game. If your opponent searched it with a card effect, and the card is in their hand, it's on you to remember that it's there. If you ask your opponent what they searched for Scarm, Malebranche of the Burning Abyss, they're NOT obligated to tell you the answer.

Other Things About Public Knowledge
Your opponent's penalty history in the tournament is not Public Knowledge. You don't get to know what infractions they've committed previously in the tournament, you can only know what's happening in your match. If you see an infraction take place, call for a judge and let them sort it out. If an infraction did take place, the judge should ask the player if they've committed the infraction before and the player is obligated to answer truthfully since lying to a tournament official is one of the definitions of Unsporting Conduct – Cheating and the penalty is Disqualification without Prize.

Face-down banished cards are not Public Knowledge. Only the player who owns the cards can see which ones they are. They may only target face-down banished cards with effects that only affect “cards” and not “monster cards”, “spell cards” and such.

The identity of cards set by the effect of Quaking Mirror Force are not Public Knowledge. However, the cards themselves have to be identified as “the monsters set by Quaking Mirror Force” since those specific monsters can't have their positions changed, so it's appropriate to use a note to remind both players of this. The note can be either a written note or an object placed on top of the card. So while you're not required to answer “there's a Gravekeeper's Spy down there right?”, you do have to properly answer “these two monsters were the ones hit by Quaking, right?”

If a card has a “you can only use/activate the effect of “X” once per turn/Duel” restriction on it, you may use a note to keep track of the effect being used, and since notes are Public Knowledge, so is the information that the effect was used.

If you have any questions about Public Knowledge, tournament policy, card interactions or game mechanics, send me an e-mail (one question per e-mail please!) to and your question could be answered in a future edition of Court of Appeals!

-Joe Frankino

Joe is a Yu-Gi-Oh! judge and player from Long Island, New York. His local once had a regular player who asked “is it game” after every action he took. Needless to say, it wasn't game most of the time.

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