Shroud of Turin Blog

Blood Clotting and the Strange Case of Brother Hirudo

– A special posting by Kelly Kearse –



The idea has been proposed that the bloodstains on the Shroud of Turin are the result of application of the blood meals of the medicinal leech, Hirudo Medicinalis, using a felt-tipped pouch. The identity of this illusory forger remains unknown, but has been suggested to be an overzealous medieval monk. For the purpose of discussion, we’ll call him Brother Hirudo. While many may view this idea so preposterous that it warrants no further consideration, this suggestion will be examined below with the focus on maintaining an objective evaluation of the specifics of this proposal. When a hypothesis is put forth, it is predictable that others will raise questions regarding the scientific merit of such ideas. This is standard operating procedure for scientific inquiry. Inflammatory rhetoric and insinuations regarding personal character should not be a part of the equation; it is destructive and takes the focus off of the science. A brief discussion of the procedure of blood clotting is introduced, followed by several specific, key questions regarding the basis of this hypothesis.

Blood clotting

There are four major components important in the clotting of blood: i) platelets, ii) red and white blood cells, and iii) a group of molecules collectively termed clotting factors, which include iv) fibrin, a molecule that forms a meshwork or web, joining all of the above together into a blood plug. When a tear in a blood vessel occurs, platelets first become activated and begin to adhere to the walls of the opening. Unless the tear is very small, platelets by themselves are not sufficient to stop blood flow. Various clotting factors are stimulated to reinforce the platelets, the main one being fibrinogen, which is converted to fibrin, creating a fibrous web that functions as a type of glue. Other cells, such as red and white blood cells may become trapped within the web and help fortify the clot.

The medicinal leech (Hirudo Medicinalis) begins feeding on human blood by

attaching itself to the skin and piercing the outer layer with a set of three blades, arranged at an angle to each other. Leeches contain a natural anticoagulant, or blood thinner, termed hirudin that interferes with the conversion of fibrinogen to fibrin (discussed above) that precludes the clotting of ingested blood. As the leech feeds, the watery portion of blood, the serum, is excluded to maximize the intake of red blood cells. Digestion of blood meals is extremely slow. Leeches may take up to several months to digest imbibed blood. Morphological preservation of erythrocytes ingested by leeches has been observed for up to 18 months.

1. Could the anatomical precision of bloodstains be accurately portrayed using leech-ingested blood applied with a felt stylus?

On average, the human body contains approximately 5 liters or 5000 ml of blood. A person may lose up to 10-15% of total blood volume (500-750 mls) without experiencing any major symptoms. (For those who may not regularly use the metric system, 16 oz. is equivalent to approximately 470 mls or 1 pint). A single leech may consume as much as 15 mls of blood in a feeding. Thus, Brother Hirudo would not have needed to expend tremendous effort to collect a sufficient volume of blood for the task. Moreover, there is no reason to assume that blood collection had to be restricted to a single event.

It has been suggested that the image on the Shroud of Turin shows no obvious, unequivocal evidence of wounds, which would be consistent with the requirement for application of bloodstains. However, various medical specialists would disagree (Barbet, 1963; Bucklin, 1997; Zugibe, 2005; Svensson, 2012; Svensson and Heimburger, 2012), asserting the presence of a major post-mortem wound on the right side of the body and puncture wounds located in the left wrist and middle of the right foot. The forensic accuracy of the bloodstained patterns on the Shroud has also been noted by numerous medical doctors and specialists spanning multiple decades, many of which are listed in the introduction of Y. Clement’s 2012 article “Concerning the authenticity of the Shroud of Turin: please don’t forget the evidence of the bloodstains!!!” For instance, Barbet noted that the blood flow follows a furrow between two extensor muscles of the forearm; others have discussed the gravitational flow of blood from the elbow and off the foot.

Is it reasonable to assume that someone like Brother Hirudo would have the knowledge to include such precise detail when creating the bloodstains on the Shroud? Relatedly, is it feasible that such clearly marked edges of the bloodstains could be achieved by delivering leech-sourced blood through a felt applicator, together with the use of a set of templates? Even the most open-minded scientific reviewer might struggle here.

The bordering area surrounding many of the bloodstains exhibits a halo of sorts, which is only visible under ultraviolet light (Miller and Pellicori, 1981; Jumper, et al., 1984). The medical doctor G. Lavoie, a specialist in internal and occupational medicine, has noted that such halos demonstrate the blood marks of the Shroud had exuded serum (Lavoie, 1998). Moreover, these data are consistent with the previous detection of blood serum proteins on Shroud bloodstained fibers by both chemical and immunological methods. It is unclear how application of leech-ingested blood might be considered here, as a paucity of blood serum would be expected in such mixtures since exclusion of serum occurs in the initial phase of leech feeding (see above). Considering that Brother Hirudo may have been visionary, foreseeing the use of uv analysis in the future, he might have set aside sufficient serum to decorate such wounds, using an additional set of specialized templates.

2. Is the presence of hydroxyproline in blood samples sufficient evidence of leech involvement?

Mass spectrometry is among the most powerful methods that exist for the identification and characterization of small amounts of substances present within a sample. To this end, pyrolysis (heating) coupled with mass spectrometry was performed on samples from the Shroud, having the primary goal of the sensitive detection of impurities (e.g. painting materials and sebum), (R. Rogers, 2008). A blood-spotted ( “Zina”) sample taken from the heel area was shown to emit hydroxyproline following treatment with low-temperature. These results helped to define an upper limit on the highest temperature the blood on the cloth was exposed to, as related to suggestions the Shroud was at one time boiled in oil (Rogers, 2008); also towards Rogers’ refutation of photons of particular wavelength playing a role in image formation (Rogers, 2008).

A tenet of the leech hypothesis is that hydroxyproline is not a regular constituent in human blood, that there is scarcely any worth speaking of. Moreover, as hydroxyproline is known to be present in connective tissue (collagen) of animals, including leeches, this can account for the hydroxyproline signal at m/e 131.

While true that hydroxyproline does not represent a principle component of human blood, its scarcity may be overhyped here. Hydroxyproline can be detected in normal human blood serum using simple immunological techniques that do not approach the sensitivity of mass spectrometry (ELISA kits, see and for examples). Using HPLC (high pressure liquid chromatography) methods, serum levels of hydroxyproline may be evaluated in patients as a measure of liver and renal function (E. Kucharz, Rom J Intern Med Oct-Dec; 32: 271, 1994; Inoue, et al. Analyst Apr. 120: 1141, 1995; Inoue, et al., Biol. Pharm. Bull. Feb 19: 153, 1996). The clinical significance of a hydroxyproline-containing protein in human plasma was reported by Carwile LeRoy and Sjorerdsma as early as 1965 (J. Clin. Investigation 44: 914, 1965). It is not a given that the presence of hydroxyproline is indicative of contamination by animal protein, i.e. leeches. Perhaps it is an oversimplification, but has it also been considered that the sample taken from the heel area could contain trace components (hydroxyproline) of abraded skin? Or that the sample might have been contaminated by exposed skin during its collection and handling? Analysis of multiple blood areas would help determine if this finding were unique to this particular area of the cloth, and further validate the detection of hydroxyproline in Shroud bloodstains.

3. What are the colorometric and chemical properties of leech-ingested human blood?

One of the main issues that is raised regarding the involvement of someone such as Brother Hirudo, is what is known regarding the properties of leech-ingested blood?

Other than trying to imagine how someone might have gotten around the problem of using normal blood subject to clotting, what empirical evidence is there that the appearance of the bloodstains is telling of leeches? This raises some interesting points as to what may be known regarding the properties of leech-ingested blood that is put to further use. For example, when expelled, does such blood eventually clot upon drying? If so, what are the kinetics and what is the appearance of such bloodstains? Have any spectrophotometric studies ever been performed to compare normal vs. leech-ingested blood to evaluate the oxidation state of hemoglobin that is present? Such information could help establish a preliminary basis for further consideration of this novel idea.

Concluding Remarks

I do not have a satisfactory explanation for why the blood on the Shroud of Turin has a red appearance. I would like to know. I am not convinced that bilirubin is the answer. I am not sure I completely understand the proposed effect(s) Saponaria treatment might have. I am willing to consider the involvement of other possibilities that involve some type of conversion of chemical bonds, by natural or even supernatural means. Leeches? It’s a creative idea, I’ll admit, but I need a lot more to go there. When I was a teenager, we used to wade out to up above our waist to use a pitchfork to remove lily pads that had overgrown on our neighborhood lake in the summer. The average leech count on each laborer was easily in the mid-thirties, upper torso to bottom toe, dorsal and ventral. I guess that’s why our dads sent us out to perform the task while they “held down the fort.” Of course, Brother Hirudo would have anticipated as much.

Whatever the pathway, the coloration of the bloodstains on the Shroud must have a definable, molecular basis. Further characterization of the chemical nature of the blood is central in any effort to define the basis for the resultant color. It is reasonable that more could be learned by careful examination of older (unrelated) blood samples. Others may argue that because this situation is totally unique, such comparisons will eventually become futile; even so, perhaps important knowledge could be gained before eventually is reached. Finally, any evaluation of blood coloration should be considered in the context of adhering to/binding the fibers of the cloth; this is an important variable, which should be part of the matrix. It is also one of the most challenging. The coloration of the bloodstains is an interesting scientific question, regardless of where one stands on possible mechanisms involved in image formation, or even on the proposed age of the cloth.

Other essays and postings by Kelly Kearse:


Guest Posting by Kelly Kearse: Distinguishing human blood from that of other species

Guest Posting by Kelly Kearse: Whose DNA is it, anyway?

Positive for AB is not the same as AB positive

MUST READ: Cloning the man on the Shroud of Turin

Just how old is the AB blood type?

MUST READ: A lot of old blood types as AB: Not Exactly