Passion relics preserve the memory of objects associated with Christ's suffering and burial. Old inventories, secure custody, and surviving textiles make their history open to investigation. In the case of the Sudarium of Oviedo and the garments of Trier and Argenteuil, historical research and materials examination work together.
Documentation, textile identification, dating, and, where applicable, blood analyses contribute different kinds of evidence. These findings are brought together for each object. Ecclesiastical tradition and the examinations each receive the place appropriate to their evidential value.
Tracing Provenance
The investigation begins with the earliest accessible accounts. Researchers distinguish a contemporary inventory, an account of a transfer, a later copy, and a tradition first recorded centuries afterwards. They check whether the description actually refers to the same object: material, dimensions, damage, place of custody, and associated container can help. A gap is made visible as a gap. A long history of veneration establishes veneration; by itself, it does not close the gap to the claimed original event.
Ecclesiastical certificates of authenticity, often called Authentica, seals, and inventories are important parts of this object history. They are read together with their issuer, date, and precise scope. A certificate may attest to the lawful removal of a fragment from a particular reliquary without thereby scientifically confirming every earlier tradition associated with that reliquary.
Document First, Then Examine
Before any intervention, a precise record is made: front and back, scale, colors, seams, folds, stains, burn marks, additions, and earlier restorations. Photographs require documented lighting and color calibration. Otherwise, differences in photography may appear to be differences in the object. Particularly fragile textiles are first examined using methods that do not consume a sample. Light, heat, mechanical pressure, and opening a historical frame can also matter for conservation. Specialists must therefore weigh the benefits and burdens in advance.[3][4]
The methods complement one another. Getty describes this combination of molecular and elemental examinations for cultural objects; current textile research shows how spectroscopy and proteomics together reveal materials and dyes. A collection of instrument names, however, does not replace a reasoned examination plan. For every test, the specific proposition to be tested must be established beforehand.[3][4][5][6][7][11]
| Method | Plain Explanation | What It Establishes and Its Limits |
|---|---|---|
| Light microscopy, including polarized light, meaning light aligned in a specific direction | Fibers, thread twist, weave, and deposits are viewed at high magnification. | Can distinguish material types, additions, or foreign particles. An old weaving technique alone provides neither a narrow date nor a person's name. |
| Imaging in ultraviolet (UV), visible, and infrared light | Different ranges of light reveal different substances and alterations. | Can distinguish image areas, stains, and retouching. A fluorescent area is not thereby chemically identified. |
| FTIR and Raman spectroscopy: identifying substances with light | Measures how substances interact with infrared light or laser light. | Provides indications of molecules, such as binders, dyes, and aging products. Mixtures, strong fluorescence, and very small quantities complicate identification. |
| X-ray fluorescence, or XRF | The measurement shows which detectable chemical elements occur at the point measured. | Iron may belong to blood, soil, or a pigment. Detecting an element does not yet identify a substance, much less a miracle. |
| Mass spectrometry and proteomics | Small molecules or protein fragments are examined by their mass and structure. | Can identify particular proteins or animal species more closely. Aging, mixing, and the introduction of modern substances must be considered. |
| DNA analysis | Surviving genetic traces are amplified or sequenced and compared. | Can investigate biological origin or mixtures. A human trace may also come from handling; without an authenticated comparison sample, it establishes no historical personal identity. |
| Radiocarbon analysis, or C14 | Measures the proportion of radioactive carbon in the organic material examined. | Dates the sample within a time interval adjusted against comparison series. Whether that sample represents the original object is a separate question. |
A Sample Must Retain Its Traceable History
A detached thread is meaningful only if its origin remains traceable. The sampling location, time, people involved, tools, packaging, transport, subdivisions, and storage must be documented. Every subsample receives a unique identifier. Controls can include unaffected areas, packaging material, or known comparison materials. A blank sample goes through the procedure without material under investigation and reveals possible contributions from the laboratory.
As far as the task allows, investigators should not know the expected religious interpretation. Such blinded examinations reduce the influence of expectations. A second examination becomes especially valuable when an independent laboratory uses other appropriate methods. Measurement uncertainty, unsuccessful tests, and contradictory results also belong in the report. This approach follows general principles of forensic quality assurance; it does not claim that historical relic examinations have always met them fully.[8][9]
Blood Is a Separate Investigative Question
A reddish discoloration is initially an observation. Establishing blood requires suitable chemical or molecular markers and their confirmation by other methods. A simple color-reaction test may be sensitive but can also react to other substances. An iron signal alone is insufficient. In old traces, degradation products may survive while other features have disappeared. A negative result can therefore be understood only in the context of preservation, detection limits, and the amount of material tested. In turn, confirming the presence of blood does not yet answer when it reached the object or whose blood it was.[10]
Ecclesiastical Authentication and the Protection of Relics
The 2017 instruction “Relics in the Church: Authenticity and Preservation” regulates in particular the handling of relics of the blessed and saints, and mortal remains in ongoing canonization proceedings. It provides for ecclesiastical authority, recorded examinations, experts, and secure custody. Its scope must not silently be expanded into an identical special procedure for all relics of Christ. For relics in general, Canon 1190 prohibits sale; for significant or particularly venerated relics, it requires permission from the Apostolic See for permanent transfer or alienation.[1][2]
During such a canonical recognition, meaning an official examination of the existing relics, appointed officials, medical experts, and witnesses act together. A notary records the proceedings. Earlier documents and seals are checked; at the end, the record and container are secured. This protects the relic's identity and dignified preservation. A scientific statement may extend only as far as the examination actually performed.[1]
Sources and procedural documents
- [1] Relics in the Church: Authenticity and Preservation
Official instruction. Its direct subject is the relics of saints and mortal remains named there in the corresponding proceedings.
Open source · vatican.va ↗ - [2] Codex Iuris Canonici, Canon 1190
Official German version; protection, transfer, and prohibition of sale.
Open source · m.vatican.va ↗ - [3] Methodologies for Instrumental and Analytical Characterization
Methodological explanation by the conservation institution conducting examinations.
Open source · getty.edu ↗ - [4] Preventive Conservation
Preservation of cultural objects and environmental influences.
Open source · getty.edu ↗ - [5] Investigation of Natural Dyes and Taxonomic Identification of Fibers Used in Chancay Textiles by Vibrational Spectroscopy and Mass Spectrometry
Original examination of historical textiles; an example of methods, not a relic examination.
Open source · pubs.acs.org ↗ - [6] Palaeoproteomics and microanalysis reveal techniques of production of animal-based metal threads in medieval textiles
Original examination of historical textiles; protein identification and contamination.
Open source · nature.com ↗ - [7] XRF Boot Camp for Conservators
Non-invasive X-ray fluorescence analysis of cultural objects.
Open source · getty.edu ↗ - [8] Forensic DNA Interpretation and Human Factors: Improving the Practice Through a Systems Approach
Forensic quality assurance; not a special ecclesiastical regulation.
Open source · nist.gov ↗ - [9] DNA Mixture Interpretation: A NIST Scientific Foundation Review
Mixed traces, contamination, validation, and limits of interpretation.
Open source · nist.gov ↗ - [10] Study of the methodological system for blood residues with different degrees of degradation on artefacts
Original experiments examining blood traces with different degrees of alteration.
Open source · nature.com ↗ - [11] Radiocarbon dating of the Shroud of Turin
Original publication by the three dating laboratories.
Open source · nature.com ↗