I've never understood why so many Christians want to believe that the shroud is genuine. If I were a Christian, I'd want it to be fake.
Why? Because the shroud is one single rectangular sheet, whereas the Bible speaks of the burial cloths of Jesus very differently:
John 19:39-40
He was accompanied by Nicodemus, the man who earlier had visited Jesus at night. Nicodemus brought a mixture of myrrh and aloes, about seventy-five pounds. Taking Jesus’ body, the two of them wrapped it, with the spices, in strips of linen. This was in accordance with Jewish burial customs.
Other relevant passages:
Mark 15:46 states that Jesus was wrapped in linen. The Greek verb used means 'press in,' "pack,' 'force in.' Matthew and Luke obviously found the word somewhat unseemly and replaced it with one that means 'envelop.' But the clear implication of all three synoptics is that the material was bound tightly round the body." The Shroud of Turin shows an image made by simply lying a linen shroud on top of the front of the body, over the head and down the back.
Luke 24:12 says that Peter observed the "...linen clothes laid by themselves..." If Jesus had not been wrapped in linen strips, but had been enclosed by the Shroud of Turin, one would expect Luke to have written that Peter saw the "...linen cloth laid by itself".
John 19:40 indicates that Jesus burial was a normal one, following the Jewish traditions. Thus, Joseph of Arimethea would have washed the body. The body shown in the Shroud of Turin was not washed.
John 20:6 repeats the events recorded by Luke; he mentions that Peter saw "the linen clothes," not the linen cloth.
John 20:7 makes a point of mentioning that there was a head covering -- a napkin -- as well as the (plural) "linen clothes." This passage describes multiple clothes. It does not match the shroud of Turin which is a single panel of linen.
The first John passage I quoted above states that Jesus was buried “in accordance with Jewish burial customs.” What were those customs? Well, Jewish burial was in some ways similar to Egyptian mummification. The body was first first coated with a mixture of myrrh and aloes. Then the body was wrapped in long linen strips that were also saturated with myrrh and aloes. Beginning with the extremities, each arm and leg was individually wound like a mummy. Then the entire body was wound from toes to neck, also like wrapping a mummy. The fully wrapped body was then coated with any remaining myrrh and aloes, while the unwrapped head was simply covered (draped) with the dead person's own prayer shawl, which was not saturated with myrrh and aloes. Within 3 days, the mixture of myrrh and aloes dries rock-hard, like shellac, producing an exceedingly stiff and solid cocoon.
This was the Jewish burial custom.
We see this also in the account of Lazarus being raised from the dead:
JOHN 11:44: The man who had died came forth, bound hand and foot with wrappings, and his face was wrapped around with a cloth. Jesus said to them, "Unbind him, and let him go."
Same as Jesus, Lazarus was wrapped with wrappings (like a mummy) which required that other persons remove (cut off) the wrappings. Rather than have Lazarus, himself, cast off the burial clothes like a bed sheet (shroud) as he arose.
So the bottom line is this: If the shroud is genuine, then the gospel accounts are fake (and Christians can kiss their beloved doctrine of inerrancy goodbye). If the gospel accounts are genuine, then the shroud is fake.
Take your pick.
Either way, the skeptics win this one.
