The Shroud of Turin is a rectangular linen cloth about 4.4 metres long that carries the faint image of a man, seen front and back as though the body had been laid on one half and the other folded over the head. The marks read as wounds to the wrists, feet, side, scalp and back, matching the Gospel description of scourging and crucifixion. Because the image behaves like a photographic negative, tonal values reversed, it became famous only after 1898, when the first photographs made the figure legible. For believers it is a witness to the passion and possibly the burial cloth of Christ; for the Catholic Church it is officially an aid to devotion rather than an authenticated relic. Whatever its origin, the Shroud has generated a substantial scientific literature and remains the most examined single artifact associated with Jesus.
The 1988 radiocarbon study that dated the cloth to AD 1260-1390 used accelerator mass spectrometry at three independent laboratories, Oxford, Zurich and Arizona, from a single sample cut from a corner of the cloth, publishing its result in Nature the following year with a stated ninety-five percent confidence range. Defenders of an earlier date have proposed the sample was contaminated by centuries of handling or by material from the 1532 fire repair, arguments the testing laboratories and most conservators have not accepted as sufficient to overturn the result. Independent of the dating question, pigment analysis by the chemist Walter McCrone argued for iron-oxide consistent with a painted image, while STURP, the 1978 Shroud of Turin Research Project, argued against paint, and no single explanation commands full agreement.