On the Shroud of Turin are many blood stains. These stains make visible the wounds of Christ. On the left side of the photo above, on the left hand is blood from one of the nails. Still on the left half of the shroud, there is a blood stain from the spear which pierced his heart. The scourge marks are easier to see on the right side of the photo, but there are marks all over the body image. On the far right and far left sides of the photo there is blood from the nail wounds on his feet. In the center, where the image of Christ’s head is, there are the wounds of the crown of thorns.
To see that these blood stains are unusual is evidenced by their color. The blood on the shroud is still red. These wounds bled from one who had gone through severe trauma. Christ had bled so much that his body was not circulating enough oxygen. To combat this state, his liver would have attempted to speed up the production of oxygen by using bilirubin, which remains red indefinitely.
Another point concerning the blood on the shroud, is its relation to the image on the shroud. X-ray studies have shown that the blood was put on the shroud first and the body image came after. There is no body image beneath the blood.
Resources: Part one of our Virtual Pilgrimage on the Shroud of Turin (coming soon to YouTube)