The Blood-Type Improbability of the Passion Relics

Those who defend these relics offer a line of reasoning that is easy to follow. Three cloths kept in different places are said to have carried blood of the same rare group. Certain extraordinary transformations of hosts are also reported to show this result. A consecrated host is bread that has become the body of Christ during Mass. Other similarities are said to strengthen this first connection.

This reasoning is part of a reasoned defence of the Catholic faith. To venerate an object means to honour it because of what it calls to mind. The reasoning does not consist of saying: “This object is venerated, so it is authentic.” It looks for clues that can be checked and that could also interest someone with no religious beliefs.

To understand the argument, let us start with blood. Researchers distinguish four main groups, called A, B, AB and O. The classification depends on markers found on red blood cells. Red blood cells are tiny parts of the blood.

Group AB has both A and B markers. It accounts for about 3 to 5% of the world's population. At 5%, that means one person in twenty. Finding this group several times may therefore be more surprising than finding a very common group.^[1]

But two people with the same blood group are not necessarily the same person. Several people can wear clothes of the same colour. In the same way, several people can have the same blood group.

The strength of the argument therefore depends on what accompanies the AB result. Defenders also point to plants from the same region and stains in matching places. They also connect the visible wounds with the Gospel accounts. It is the agreement between these elements that they find particularly convincing.

Scientific critics offer another explanation. Perhaps some tests give the same result because they encounter the same difficulty on ancient objects. In that case, the repeated result would not necessarily show a common origin. This objection deserves a precise answer.

Both approaches can at least begin with a shared rule: distinguish an observation from its interpretation. Seeing a reaction in a test is an observation. Saying that it reveals the blood of Jesus is a much broader conclusion. Several steps between the two need to be checked.

A laboratory analysis involves examining material with suitable instruments and substances. Researchers generally remove a very small amount from the object being studied. This small amount is called a sample. What it allows them to conclude depends on where it came from, its condition and the checks carried out.

The objects being examined are thought to have served different purposes. The Tunic is thought to have been worn before death. The Sudarium is thought to have covered the face on the cross and then while the body was being moved. The Shroud is thought to have wrapped the body in the tomb.

This difference matters a great deal. We are not comparing three copies of the same image. We are comparing traces that the same body could have left at successive moments. It is a little like retracing someone's movements through several objects used during the same day. A shroud is a cloth used to wrap a dead person.

The Holy Shroud of Turin is a large linen cloth. It measures 4.42 metres long and 1.13 metres wide. It bears an image of the front and back of a dead man. His wounds match those of a man who was whipped, crowned with thorns and crucified.^[2]

The Gospels mention the shroud in which Jesus' body was placed. The identification of the Shroud with this cloth rests on its appearance, its wounds and its history. Its presence in Lirey, in the Champagne region, is documented in 1357.

The team that examined the Shroud in 1978 also studied the image of the body. It concluded that the image was neither a painting, a drawing nor a burn. It did not determine how the image had formed.^[3]

The Sudarium of Oviedo is much smaller: 84 by 53 centimetres. It is kept in Oviedo Cathedral, in Spain. Unlike the Shroud, it bears no image of the body. It has stains of blood and other fluids.^[4]

The name Sudarium refers here to this face cloth. Tradition connects it with the cloth that had covered Jesus' head, mentioned by Saint John. Its history is told in ancient chronicles. A formal opening of the chest containing the relics is documented in Oviedo in 1075.

The doctor José Delfín Villalaín Blanco studied how its stains formed. He describes blood mixed with pleural fluid. Pleural fluid is fluid from the area surrounding the lungs. In his interpretation, this mixture matches the condition of a man who died by crucifixion.^[5]

He distinguishes stains formed when the head was upright from others formed after it was moved into a horizontal position. This sequence fits the move from the cross to the carrying of the body. It does not identify the dead man. It establishes a match between the traces and the events of the Passion.

The Tunic of Argenteuil is a woollen garment kept in France. It was originally woven without seams. Saint John specifies that Jesus' tunic had this feature. The first undisputed written mention of the Argenteuil relic dates from 1156.

The garment has had an eventful history. In 1793, the parish priest Pierre-Jean Ozet cut it up in an attempt to save it during the French Revolution. Fragments were buried, then recovered. In 1795, twenty pieces were sewn back together on satin.^[6]

These events explain why the object as it exists today requires so much care. Researchers are examining a garment that has been cut into fragments, handled and reassembled.

Its thread is twisted to the right. Many Jewish textiles from Jesus' time have thread twisted to the left instead. This difference needs an explanation, but is not enough to rule the object out. The biblical rules cited forbid mixing wool and linen in a garment. They do not forbid pure wool.^[7][8]

Two questions need to be kept separate: do the stains contain human blood? And, if so, what group is it? An examination can answer the first without resolving the second. Confusing these two steps would give the results more weight than they deserve.

On the Shroud, John Heller and Alan Adler identified several substances characteristic of blood. Their work addresses the explanation that the red stains are simply paint. They acknowledge tiny traces of pigments. Pigments are colouring substances. But their distribution does not support this explanation of the bloodstains.^[9]

Pierluigi Baima Bollone investigated the blood group. In 1982, his team announced an AB result. Further examinations followed in 1984. The method involves looking for A and B markers using substances that recognise them.^[10][11]

These markers are called antigens. Here, an antigen is a structure that the testing substance can recognise. The substances used contain antibodies. An antibody is a substance that can attach itself to certain markers.

Researchers can make this attachment visible using a dye that glows under suitable lighting. They then observe the fibres under a microscope. A microscope is an instrument that allows us to see things too small for the eye. The reaction they observe leads them to classify the blood as AB.

The checks do not focus only on the stains. Some stained fibres react to the substances that recognise A and B, while unstained fibres do not. This comparison is a control. A control helps check that the test is responding to what researchers are looking for, rather than something else.^[12]

For the Sudarium, announcements of blood group AB date from 1993 and 1994. The first analysis is attributed to Carlo Goldoni working with Villalaín. The second was carried out by Baima Bollone on seven fragments. The same result is reported for these different samples.

However, a limitation in the documentation needs to remain clear. We know these results through Mark Guscin's overview, published in 1998. The original publications detailing these blood-group tests have not been found. These are therefore analyses reported by another source, rather than reports that can be checked directly.^[13]

For the Tunic, the first examinations remained unpublished. Their results are passed on second-hand, with no original report available. They therefore cannot count as independent confirmations. Information repeated in several accounts does not become several pieces of evidence for that reason alone.

The work of Gérard Lucotte and André Marion is presented in a book published in 2006. In it, Lucotte reports human blood and group AB. He also describes small, dried-out red blood cells. These observations support the presence of blood, but do not determine its group on their own.

Lucotte also reports extracting human DNA. DNA is material in the body with certain features that allow human traces to be compared. He interprets his results as supporting a single person as their source. This conclusion still needs confirmation, especially because his account also acknowledges recent human traces.

The book was not reviewed in the way an article submitted to a specialist scientific journal would be. Nor does it compare the DNA of the three relics. Lucotte expresses his personal conviction in these words:

“I see the whole Passion through the microscope.”

Gérard Lucotte, a researcher who studies DNA.^[14]

This conviction is striking. However, it does not replace the missing steps in the checking process. The presence of the same blood group and the identification of the same person remain two different claims.

Blood is only one part of the case. Other researchers have examined plant traces and the positions of stains. These studies interest defenders of the relics because they raise different questions. An explanation of the blood test does not automatically account for the other observations.

Pollen is a very fine dust produced by plants. Grains can remain on fabric and be examined under a microscope. Identifying the plants involved can give clues about the regions the fabric has passed through. It is like trying to work out where a garment has been from the traces left on it.

Max Frei began this research on the Shroud. Later work by Avinoam Danin and Uri Baruch re-examined his identifications. They reduced the number of species considered certain. Nevertheless, they maintained that the connections with the Palestinian region remained of interest.^[15][16]

Other surveys concern the Sudarium and the Tunic. Two plants are reported on all three cloths: the Palestine pistachio and Hampe's tamarisk. The documents do not all carry the same weight. For the Tunic, the results come in particular from Lucotte and Marion's book.

On the Sudarium, the pollen surveys also match several stages of the journey described in the chronicles. In particular, they point to Jerusalem, North Africa, Toledo and Spain. This agreement between plant traces and the account of the journey strengthens interest in the case.^[17][18]

These plants point towards the eastern Mediterranean. This region is the eastern part of the Mediterranean world. They do not grow only in Palestine. Hampe's tamarisk, in particular, grows as far as Sicily. Presenting them as an exclusively Palestinian signature would therefore be inaccurate.^[19][20]

According to the floras cited, neither of these plants grows naturally in Spain, France or mainland Italy. Floras describe the plants found in the regions they study. It is the contrast with the places where the relics are kept that attracts attention.

Yet the connection still carries weight. Plants from the same broad region are reported on cloths kept separately. For defenders, a deliberate fabrication would have to account for these details, which would be difficult to arrange without the necessary knowledge. The argument therefore needs to be examined in its own right, beyond the discussion of blood alone.

The positions of the stains offer another comparison. Alan D. Whanger overlaid images of the Shroud and the Sudarium. He reports 70 points of correspondence on the front and 50 on the back. This gives the often-quoted total of 120 points.^[21]

These comparisons concern, in particular, the marks at the back of the skull, the wound on the right cheekbone and the length of the nose. The number refers to similarities between shapes and positions. It does not mean 120 independent examinations. The results were presented at a congress in 1994, then reported by Guscin. They have not been reproduced in an independent laboratory.

Marion, for his part, compared the Tunic with the Shroud. In his analysis, the bloodstained areas on the back match wounds visible on the burial cloth. The shoulders also bear traces consistent with rubbing against the cross. The garment and the burial cloth would thus offer two complementary views of the same suffering.^[22]

Finally, the surgeon Pierre Barbet studied the wounds on the Shroud. A surgeon is a doctor who performs operations. He identifies nail wounds at the wrists and many whip marks. He also describes bleeding across the whole scalp. The crown would therefore have covered the head, rather than forming a simple ring.^[23]

According to Barbet, a nail through the palm would risk tearing the hand under the weight of the body. He sees the mark at the wrist as a precise medical detail. He also notes the spear wound on the right side, in the place expected in his reconstruction.^[24]

For Barbet, these details reveal very precise knowledge of a crucified body. Explaining these details as the work of a medieval artist would require a great deal: the artist would have had to understand and depict all these features. Yet this medical consistency does not, on its own, give us the man's name.

The veil of Manoppello is sometimes added to these comparisons. Heinrich Pfeiffer argued that its face matched the one on the Shroud.^[25] No blood-group result for this veil is presented in this case. The veil can therefore be included in a discussion of images, but not in the calculation involving blood.

A probability expresses the chance of an event happening under specific conditions. It is valid only if those conditions are chosen correctly. This is why an impressive calculation can be mathematically correct but poorly suited to the objects being studied.

Let us take an AB frequency of 5%, or one person in twenty. Let us choose three people at random from a population in which 5% have group AB. Each choice must be independent of the others.

That gives one in twenty, then one in twenty, then one in twenty. Twenty times twenty times twenty is eight thousand. We get a one-in-eight-thousand chance that all three have group AB. This is the illustrative calculation proposed for the Shroud, the Sudarium and Lanciano.

The calculation draws attention to an uncommon coincidence. It does not give the probability that the relics are authentic. These are two different questions. A figure describing an expected result does not directly measure the truth of an entire story.

Bacteria are tiny living organisms. The first condition concerns independence. Results are independent when no shared cause produces or distorts them together. If several tests react to the same bacterial presence, their agreement no longer represents several separate coincidences. It may reflect a single problem repeated.

The second condition concerns the frequency chosen. The figure of 3 to 5% describes a rough worldwide frequency today. The surveys cited give about 7% in modern Jewish populations. They do not tell us the exact frequency among people living at the time of Jesus.^[26]

Choosing a higher frequency makes the coincidence less rare. It would therefore be misleading to use the worldwide figure as a certain measure of the setting of the Passion. We do not have the necessary ancient data. The calculation remains an illustration, rather than a precise reconstruction.

The third condition concerns the reliability of the tests themselves. A result wrongly classified as AB would weaken the whole argument. Levels of documentation matter too: the Sudarium results are known indirectly. Those for the Tunic cannot be added as though they had all undergone the same checks.

Some texts announce far smaller chances still. However, they combine cases of unequal weight, sometimes without an established AB blood group. These large figures are not used here because they mix results of different quality. Their dramatic effect does not make up for the missing conditions.

The sound conclusion is therefore simpler. Several matching reports of an uncommon blood group already form a remarkable connection. They give serious reasons to consider a shared history, while still requiring confirmation of the tests. To identify the same person, however, much more precise features would have to be compared.

Here, Eucharistic miracles concern extraordinary physical transformations involving consecrated hosts. Catholic faith affirms this presence even when no visible transformation takes place.

In the cases studied, fragments that had turned red or taken on the appearance of flesh were examined. Defenders of the relics connect these results with the blood reported on the cloths. This connection requires the same care with documentation. The five cases often cited do not provide five confirmations of group AB.

The oldest is Lanciano, in Italy. The account places the transformation of a host into flesh and wine into blood clots around 750. The preserved material was examined by Odoardo Linoli. His 1971 report identifies human heart tissue and concludes that the blood group is AB.^[27]

Heart tissue is the material that makes up the heart. This identification therefore concerns the nature of the flesh examined. The determination of the blood group is another result in the report. A new examination by Linoli in 1981 reached the same conclusions.^[28]

Buenos Aires is a different case. In 1996, a host placed in water turned red. The analyses report human heart tissue and blood. But group AB, often claimed in popular presentations, is not established in the checked sources used by the recent scientific study.^[29]

For Tixtla, in Mexico, the event dates from 2006. The presence of human haemoglobin is established. Haemoglobin is a characteristic component of blood. Group AB is reported, but without a detailed publication allowing the expected checks.

Sokółka, in Poland, concerns a host transformed in 2008. The examinations report heart tissue showing signs of suffering. In Legnica, also in Poland, the event dates from 2013. Human heart tissue and DNA are reported.

For these last two cases, no AB blood group is established in a checked source. The observations about the flesh remain interesting in their own right. They simply cannot be used to complete a series of blood-group results. Saying “heart tissue” is not the same as saying “AB blood”.

The findings are therefore clear. Lanciano provides a published AB result. Tixtla provides a reported AB result. Buenos Aires, Sokółka and Legnica cannot be counted as established confirmations of this group.

This distinction preserves the real strength of the case. The heart tissue reported in several cases remains striking. The connection with the Passion also deserves attention. But no sufficiently precise comparison has yet shown that these different materials came from a single person.

The main modern criticism comes from Kelly P. Kearse, a Catholic scientist. His article appeared in a scientific journal in 2024. He does not question the spiritual value of the relics. He examines what the tests actually allow us to claim.^[30]

Some bacteria carry structures resembling the markers used to determine blood groups. A testing substance can then react without identifying the correct source. The test gives a positive result, but the result is misleading.

This difficulty particularly affects ancient objects that have been exposed and handled for a long time. Here, the word contamination means the addition of foreign material to the object. This may include bacteria or traces left by people. A result obtained today therefore does not necessarily come from the ancient trace being sought.

“AB antigens are not unique to human red blood cells: they are also expressed by bacteria, which provides a convenient link between such varied objects. A sample may thus test positive for AB without any red blood cell even being present.”

Kelly P. Kearse.^[31]

This is not an objection invented to dismiss the relics. Adler himself, who had helped identify blood on the Shroud, had pointed out this risk. On the Sudarium, a reaction corresponding to B was even observed in unstained areas. This observation calls for further checks.

The defenders' response has several parts. First, not all the examinations are limited to an A or B reaction. They also look for human blood by other means. Lucotte even reports DNA extracted from human cells on the Tunic.

A bacterium does not produce this human DNA. If its age were confirmed, it would therefore be important evidence against an entirely bacterial explanation. But the presence of human DNA does not automatically settle the question of blood group. The source of each result still needs to be checked.

Moreover, recent human material can be deposited on an ancient object. The DNA reported by Lucotte therefore needs a new independent analysis. His book itself acknowledges recent traces. The bacterial objection thus has a limit, without having already been disproved for the whole case.

Defenders then point to the controls used and the repeated examinations. Above all, they stress the pollen, stains and wounds. A bacterium does not directly explain the positions of all these traces. The investigation must therefore continue across all the clues, rather than focusing only on a chemical reaction.

Another difficulty concerns the original publications. A peer-reviewed journal has articles examined by other specialists before publication. Some journals are also listed in scientific databases. According to Kearse, none of the earlier blood-group results for these three cloths had been published in such a journal before 2024.

The results were shared in specialist journals, at congresses or in books. Franco Serafini defended their historical value in the same journal as Kearse in 2025. He points out that the techniques used had already served in other investigations. He also stresses the comparisons between stained and unstained fibres.^[32][33]

Kearse replies that success elsewhere is not enough to guarantee a reliable result on these objects. The relics have been handled for a long time and exposed to the addition of foreign material. The conditions in which they have been kept therefore require particular checks.^[34]

The debate remains open, with arguments on both sides that can be examined. Its publication finally allows this discussion to take place in a peer-reviewed journal. It does not retrospectively validate each of the earlier analyses.

Dating seeks to determine an object's age. Carbon-14 dating is an analysis used for ancient materials such as textiles. It has been applied to all three relics. The results give ages later than the time of Jesus.

This difficulty must be presented honestly. Taken at face value, these dates do not support an origin at the time of the Passion. Defenders reply that the pieces analysed may have undergone changes. As with the blood, we therefore need to look at what was actually measured.

For the Shroud, three laboratories announced in 1988 that it had been made between 1260 and 1390. These results were published in the journal Nature. They therefore form an important objection to an ancient origin. They have not been officially withdrawn.^[35]

However, the sample came from a single corner of the cloth. Raymond N. Rogers later observed cotton and chemical differences in threads from this area. He interprets these as signs of a repair. His 2005 study therefore argues that the piece may not properly represent the original fabric.^[36]

A comparison with a mended garment helps explain this. Dating an added patch does not necessarily give the age of the whole garment. But it still has to be established that the piece analysed really came from a repair. This explanation remains disputed and cannot be presented as an admission by the laboratories.

In 2022, Liberato De Caro and his team proposed another study, using X-rays. Their method examines the ageing of the linen material. The result is consistent with an age of about two thousand years. It challenges the medieval dating without disproving it on its own.^[37]

For the Tunic, two analyses give different periods. The 2004 analysis indicates 530 to 650. The 2005 analysis indicates 670 to 880. These periods are estimates with a margin of uncertainty, rather than absolutely certain limits. The two reported periods do not overlap, which calls for an explanation.^[38]

Defenders point in particular to the fragments sewn back together on satin after the Revolution. Serafini also stresses that the two measurements concern the same fragment. The precise cause of the difference remains difficult to establish. This disagreement weakens an overly simple reading of the results, but does not provide an ancient date.^[39]

For the Sudarium, the 1990 analyses agree on a date around the year 700. Researchers who support its authenticity point to particles from fires. One study examines the amount of more recent carbon needed to shift the date in this way. It therefore proposes a possible way in which the result could have been affected.^[40]

But showing that a change is possible does not prove that it happened in the amount required. This distinction matters just as much as in the study of blood. The dating results should neither be ignored nor turned into a verdict that takes no account of the examination of the samples.

The overall question remains open. The earlier results pose a real difficulty, and the challenges to them still require checks. None of these discussions alone provides a certain date at the time of Jesus. Carefully chosen new samples would allow progress.

The most important missing step is a direct comparison between the relics. Finding AB means recognising a shared category. To identify the same person, much more precise features of their DNA would need to be compared. This work has not been published for the three cloths.

Lucotte's study concerns the Tunic alone. Even if it established beyond doubt the presence of blood from a single person, one question would remain unanswered. Would the traces on the Shroud and the Sudarium also come from that person? Without a comparison between the objects, the connection remains incomplete.

Tests called STR tests compare short repeated sections of DNA. Markers called HLA are other human features that researchers propose comparing. Here, a marker is a recognisable feature used to compare traces.

Several laboratories could receive the samples under codes. They would not know which relic each piece came from. This method reduces the risk that expecting a result might influence the examination. In a double-blind study, the origin of the samples is hidden from the people carrying out and evaluating the tests.

A new programme of analysis should also distinguish human blood markers from similar bacterial structures. It should separate ancient traces from recent additions. For dating, researchers would need pieces taken far from repairs. The chemical condition of the fibres should be examined at the same time.

Finally, the methods, controls and detailed results would need to be published. Other teams could then discuss them and try to reproduce them. Confidence would no longer rest only on a researcher's reputation. It would rest on work that could be checked.

Even a shared biological identity would not be enough, on its own, to identify Jesus. It would first show that several traces came from the same person. Historical identification would still require comparing this result with the history of the objects and the wound marks they bear.

This investigation concerns the material examined. To recognise a miracle, the Church also examines whether the event can be received as a sign given by God. The two approaches can inform each other without being confused. For defenders of the relics, asking for better tests is a way of taking the clues seriously.

The Church distinguishes the value of relics from the foundation of faith. A dogma is a truth that the Church requires Catholics to believe. The authenticity of the Shroud, the Sudarium or the Tunic is not a dogma. Their veneration is one of the ways people pray and express their faith.^[41]

Our gaze does not stop at the fabric, the chest or the stains. It turns towards Christ and his Passion. Saint Augustine explains what a sign is in these words:

“For a sign is a thing which, over and above the impression it makes on the senses, causes something else to come to mind.”

Saint Augustine, De Doctrina Christiana, Book II, Chapter 1.^[42]

In other words, the fabric draws our attention, then makes us think of Christ. This takes nothing away from the importance of the physical truth. Asking whether an object really touched Jesus remains a legitimate question. But Christian life does not depend on the result of a test. It rests on the Resurrection of Christ, proclaimed by the Apostles.

“and if Christ has not been raised then our preaching is useless and your believing it is useless.”

Saint Paul, 1 Corinthians, 15:14, Jerusalem Bible.^[43]

Paul then affirms that Christ has risen. He does not offer a blood-group classification as the foundation of this proclamation. A future revision of the analyses would therefore not change the Catholic faith. It would change our judgement about certain physical clues.

This freedom allows us to welcome favourable results with gratitude while continuing the necessary checks. It also applies to other cases involving physical signs, such as Our Lady of Guadalupe. Wonder and careful examination can go forward together.

Saint Alphonsus Liguori invites us to contemplate Christ's wounds as a way into his heart. There, he helps us discover an infinite love.^[44] It is towards this love that the cloths of the Passion ultimately lead. Their traces speak of suffering, but their Christian meaning is that of a love given to the very end.

• Group AB is uncommon. Finding it on several objects deserves attention.
• The results do not all have the same level of documentation.
• Lanciano has a published AB result; Tixtla has a reported result.
• Pollen, stains and wounds provide other important connections.
• A bacterial source can distort some tests. Controls remain essential.
• No published comparative examination has identified the same person on all three cloths.
• The dating results are disputed. Catholic faith does not depend on how the debate is resolved.

The case is richer than a single surprising number. It brings together human blood, matching reports of group AB, plants and wound patterns. Their agreement provides serious grounds for a shared history connected with the Passion. In other words, these connections give reasons to think that the objects could be linked to this same history. They do not yet prove either a common biological origin or the identity of Jesus.

We can therefore take an interest in the relics while maintaining scientific standards. We can also recognise the limits of the analyses without dismissing the connections they have revealed. Believers can welcome these clues as signs God gives them to turn their gaze towards Christ. Faith does not depend on their confirmation.

For pilgrims, these cloths point above all to Jesus. They remind us that the Passion was lived in a real body, with real wounds. Science can shed light on these traces. What they invite us to contemplate remains the love of Christ, who gave his life for us.