For a correct interpretation of the data currently at our disposal, given the extensive literature on the subject, we must start from scientifically rigorous elements. In 1981, the Shroud of Turin Research Project (STURP) stated in its scientific conclusions that “The blood stains are composed of hemoglobin and also give a positive test for serum albumin.” Indeed, Heller J.H. and Adler A.D., two scientists from the STURP, managed to identify the stains as blood belonging to the order of primates (the order of placental mammals that includes humans, monkeys, and other species).

The aforementioned authors reached these conclusions by identifying the presence of hemochromogen (a substance obtained from the denaturation of hemoglobin), cyanohemoglobin (a compound of methemoglobin and cyanide ion, for which the former shows high affinity, indicating the presence of hemoglobin, a protein found in red blood cells), albumin, globulins, bilirubin, and biliverdin (a precursor of the former).

In this regard, due to the limited resources at the time, which did not allow for extensive tests to assess cross-reactivity with other species belonging to the order of primates, the authors declared that they had checked for the possibility of serological cross-reactivity with a limited number of species. These studies were conducted on the serum halos due to the quality of the stains that had formed on the cloth. In fact, the stains are not made of whole blood but from the imprint of clots, while the serum liquid, which oozed from these clots, forms the surrounding halos. For such an impression to be transferred, it must occur on a substrate (in our case, linen) within two hours of the clot formation. Only in this phase is it possible to transfer the stain in a defined manner and not as a simple smudge. The generic diagnosis of blood was made by positively testing for proteins and mineral elements that are normally found in blood, in the serum halos surrounding the stains, and not on the stains themselves.

The serum present in the halos derives from the clot at a specific moment of its formation. It is noteworthy that the description of the coagulation process began in 1835 and was only completed in 1905. Blood coagulation evolves through the phases of: (a) clot formation, (b) clot retraction, (c) clot drying, (d) fibrinolysis, and (e) drying of the stains. The transference of blood traces to the fabric occurs during the fibrinolysis phase, which in the living can vary from 2 to 4 hours, while in the corpse, it takes place within 24-36 hours after death. Consequently, on the Shroud, there are stains transferred from a clot without the clot itself being transferred, making the search for blood cells difficult. Furthermore, a small amount of cellular material may be degraded due to the time elapsed and the preservation methods.

In addition to this initial data, we must note that previous research on the antigenic profile (i.e., the search for specific proteins that unequivocally characterize the blood belonging to the human species depending on the positivity and negativity of the antigen-antibody reaction) was considered as indirect but not specific confirmation of the human nature of the traces analyzed. The identification of species on ancient blood traces, presumably whole (and even worse on stains of ancient blood clot imprints), appears rather challenging due to qualitative-quantitative issues: elapsed time, hemoglobin denaturation, scarcity or absence of cellular elements in the analyzed samples, previous exposure to physical-chemical agents, feasibility of blood rehydration for ancient samples, amount of material actually examinable, evidence of false positive and false negative results, and lastly, the possibility of using samples purified from any contamination.

In conclusion, according to the preponderance of evidence, it can be considered that the blood stains found on the Shroud fabric belong to the man whose image is imprinted on the cloth. This consideration is justified by the synthesis of both morphological and physico-chemical data. Indeed, regarding the morphological data, there is evidence that the Shroud image of the body represents that of a cadaver of a tortured and crucified man from whose wounds blood has flowed, and that the image itself cannot be attributed to painting, printing, scorching from a bas-relief, or rubbing with an interposed medium, as proven by spectroscopic, fluorescence, X-ray, thermographic, spectrometric, Raman, and microchemical tests.

As for the physico-chemical data, scientific evidence has shown that substances compatible with human blood have been identified in the serum halos. Additionally, it has been recently proven that the carmine-red coloration, instead of the usually expected brown or black, is the result of the action of ultraviolet rays (e.g., emitted by the Sun) on blood stains with a high bilirubin content due to post-traumatic hemolysis and methemoglobin, the latter being a degradation product of oxidized and aged hemoglobin typical of ancient blood.

However, it should be noted that these experiments have shown that blood stains with a high bilirubin content after exposure to UV rays maintained the carmine-red coloration for no more than four years. From what we have said, it is evident that each scientific result raises new questions and exciting challenges, fully supporting Paolo Di Lazzaro’s thesis that, from a scientific perspective, the Shroud is a “complex and elusive object.”

From: Walter Memmolo, M.D., Francesco De Micco, M.D.: Le macchie di sangue sulla Sindone, in SINDON N: 1-settembre 2020, pagg. 48-50.