To say that the Shroud of Turin is a widely known supposed relic of Christianity is to do it a disservice. Of the hundreds of supposed relics that have come and gone through-out the ages including pieces of Noah’s Ark, splinters of the True Cross, vials of tears, nails, crowns of thorns as well as more than forty other shrouds, the Turin Shroud has endured and attained world wide fame. The Shroud turned up for the first time in history in the mid 14th century and was the subject of considerable suspicion by a Bishop who found it to be central to a faith healing scam. Further, during this time the artist was found that confessed to creating the forgery.
In more modern times the Shroud has been scrutinized by science and found to be wanting. In the first instance the weave of the cloth was one that, while common in the 14th century, there is no evidence was used in the 1st. Also, while there is no pictorial record of what Jesus looked like the shroud follows the common artistic representation. In keeping with this the portrait seems to be unrealistically stylized, in that the hair hangs as for a standing figure rather than reclining and there are no distortions that would be attributable to the cloth being wrapped around a body.
Finally, radiocarbon dating of the Shroud gives a range of 1260-1390CE, suspiciously close to the time the relic appeared and the confession of the artist implicated in creating the forgery (circa 1355CE). Despite the contrary evidence there is no shortage of those who defend the Shroud as authentic. Perhaps in time this too will go the way of previous relics, but I doubt it.