I am convinced the "tests" were a fraud. The Shroud is real.
Let's be perfectly clear: carbon 14 dating is an excellent and very accurate scientific method for determining the age of many things as old as 50,000 years.
The failure to obtain a reliable date for the Shroud of Turin is not about flaws in carbon 14 dating methods or contamination. It is not about the problems, so often discussed in the media, of mysterious biological polymers growing on the cloth's fibers or new carbon introduced into the Shroud's cloth by a scorching fire in 1532.
It is not about the sloppy work by three very prestigious carbon 14 dating laboratories. And it is not, as some suggest, about conspiracies dreamed up to prove religious or anti-religious arguments (the Shroud is a religious object for some).
It is about a stupid mistake.
From National Geographic News, PBS and several scientific papers, we learn that the carbon 14 dating of the Shroud of Turin was done with an invalid sample. This is now being confirmed in a peer-reviewed scientific journal: Thermochimica Acta. The article, accepted in final form, is available on Elsevier BV's ScienceDirect® online information site. Elsevier is one of the world's largest providers of ethical, peer-reviewed scientific, technical and medical literature. The abstract reads in part:
"Preliminary estimates of the kinetics constants for the loss of vanillin from lignin indicate a much older age for the cloth than the radiocarbon analyses. The radiocarbon sampling area is uniquely coated with a yellow–brown plant gum containing dye lakes. Pyrolysis-mass-spectrometry results from the sample area coupled with microscopic and microchemical observations prove that the radiocarbon sample was not part of the original cloth of the Shroud of Turin. The radiocarbon date was thus not valid for determining the true age of the shroud."
The problem is called material intrusion. It is an uncommon problem in some carbon 14 dating exercises. For instance, in dating peat bogs, which may be very old, the samples often contain miniscule roots from newer plants that grew in the peat. Sometimes the roots, having decomposed, are indistinguishable from the older peat. What is tested might simply be a mixture of old and new material leading to erroneous results. No one expected that material intrusion might be a problem with the Shroud of Turin. But it was. By some estimates, as much as 60 percent of the Shroud of Turin sample was new thread, the result of mending in the 16th century. This is sufficient to change the date of a 1st century shroud to the medieval date range arrived at by the carbon 14 dating.
M. Sue Benford and Joseph G. Marino, with the help of several textile experts, undertook a detailed examination of the documentation photographs of the carbon 14 samples and identified clear indications of a medieval patch.
Independently, Ray Rogers, a Fellow of the University of California, Los Alamos National Laboratory and a charter member of the Coalition for Excellence in Science Education has examined actual threads and fibers adjacent to where the samples were snipped. In a paper he published with Anna Arnoldi of the University of Milan, Rogers reported finding indisputable chemical evidence of a repair patch. He found dyestuff and spliced threads. Others, using scanning electronic microscopes and advanced spectral analysis tools have confirmed his findings.
Carbon 14 dating is an invaluable tool for archeology and science. The mistake made in dating the Shroud of Turin does not diminish this fact.
For more information see Why No One Can Explain the Pictures of Jesus on the Shroud of Turin and Shroud of Turin Guide to the Facts 2005