I have been working on a mentalism piece that goes like this:

The magician walks up to a spectator and hands them the deck. They shuffle, select a card, and put it on top. The magician shuffles the deck, then the spectator shuffles the deck. Finally, the magician hands the spectator the deck and tells them to choose. They can take out their card and hand it to you, or they take out a card and tell you it is their card. The magician subsequently reveals whether or not it is their card, and, if it is not, locates their card.

Is this effect original, and if not, who created it?

As a better question: Is it a good effect?

In my honest opinion - no.

Way too much process for what is essentially a lie detector. Why all the shuffling? Other than it provides the opportunity for you to glimpse their card, of course.

The key to mentalism is that it should feel real. In my opinion, for this to feel real it would work much better if you did it this way - Spread the deck across the table. Have them look at the cards and mentally select one without indicating it to you. Then have them push one card toward you, and you will tell them if it's the card they mentally selected or not.

If you're worried about them lying, having them either whisper it to another audience member, or write it down under the table.

Thank you so much fo the honest answer.

What if I eliminate all the shuffling. They select the card, put it in the deck, and put the deck in their pocket. Then you have them lie, and reveal their card. Or simply make it body language based and say, "red black red black", and so on.

I keep going back to "Why?" for this.

What is the purpose of having them take a card out, look at it, put it back and hide it on themselves? Other than to give you a moment to get a peek or read a mark, of course.

What power are you displaying? If you can detect lies, why not have them just think of a card's value? The physical process that you are describing makes no sense, other than to provide a moment for a method to be used.