There are several theories how Charny got possession of the shroud.
According to the D’Arcis memo, he got it from a forger.
procured for his church a certain cloth cunningly painted, upon which by a clever sleight of hand was depicted the twofold image of one man, that is to say, the back and front, he falsely declaring and pretending that this was the actual shroud in which our Saviour Jesus Christ was enfolded in the tomb, and upon which the whole likeness of the Saviour had remained thus impressed together with the wounds which He bore.
Eventually, after diligent inquiry and examination, he discovered the fraud and how the said cloth had been cunningly painted, the truth being attested by the artist who had painted it, to wit, that it was a work of human skill and not miraculously wrought or bestowed.
Again, no name of the forger was produced, so it’s pretty much a useless claim.
Another theory is he got it as a gift from King Philip.
Geoffroy, knight, Count of Charny and lord of this place Lirey … received from King Philip as recompense for his valor, the Holy Shroud of Our Lord … with a generous portion of the true cross and several other relics and sanctuariums, to be placed in the church which he hoped to build (Scavone 1993: 208-09).
It’s highly doubtful if King Philip had possession of it. Even if he did, it’s highly doubtful he’d give it to a lowly knight as a gift. Simply a piece of the True Cross would’ve already been considered an extremely gracious gift.
Further, the above two theories still do not explain how the image on the cloth was created.
Another theory, and the most popular, is from Ian Wilson.
No other theory of how the Shroud came to Geoffrey de Charny is better known than that advocated by Wilson’s 1978 The Shroud of Turin, and for good reason.
I’ll talk more about this much later when I discuss the history of the shroud.