Method
You say “In this trick, you can either tell the T-R-U-T-H (putting 1 card on top of another on the table for each letter), or you can L-I-E (do the same)”.
Ask them to pick a card from the remaining cards. When they have done so, discard the remaining cards. Put the top 2 cards on the table on on top of another, and ask them to put their card on the remaining pile in your hand. Put the 2 cards back on top. Then say “Now tell me the number of your card. You can tell the truth or lie”.
They do so, and you put one card on the table for each letter. Put the remaining cards straight on top of the pile. Spell out O-F with the cards and put the remaining ones on top, then ask for the suit, reminding them they can lie. Spell it out and put the remaining cards on top. Then say “now, even if you lied, the cards always tell the T-R-U-T-H“. Spell out the cards, and turn the card on the H count over. It is their card.
Trick by Erin Veazey