I saw the photographer that was hired to examine the Shroud. He was non Messianic Jewish. He said “I went in there saying we will know within 10 minutes if they used pigmentation or heat to create the image....but after 6 months of studying and examining it, we had absolutely no idea!”
He said his biggest reason for believing it was not genuine was because the blood was reddish and not blackish as you would explain. He said years later he asked a friend that was a hematologist if blood ever dries red instead of black. His friend said that in rare cases when a victim in horribly , the body releases bilirubin in the blood which would cause that. After hearing that, he became 100% convinced it was real.
The Shroud even shows stains from nail-marks in the WRISTS, not the hands. In Greek the word for hand...includes the forearms. So when the Bible says Jesus had marks on his hands after the resurrection...it doesn’t mean the palms.
Medieval artists though, did not know this, so you ALWAYS see depictions of the crucifixion with nails going through the palms. Testing was done around 1900 with cadavers in France. Without additional support, like tying the arms to the cross, nails in the palms simply (excuse the image) rip out... Physically, nailing a man like that to a cross doesn’t work.
HOWEVER, if nails are (most painfully) put through the wrists, or, in between the radius & ulna bones (in the forearm) a body CAN hang on a cross, and not fall off. And in the wrist area...is exactly where the Shroud shows the nails. Unknown to anyone really, for 1600+ years, since the Romans stopped crucifying people....
For years, I kept a shirt with blood splatters that remained bright red so know that part is true.