Scientists

Scientists have indeed tested the Shroud of Turin. ln 1969 the Archbishop of Turin appointed a secret commission to examine the shroud. That fact was leaked, then denied. The commission included internationally known forensic serologists who made heroic efforts to validate the 'blood', but all of the microscopic, chemical, biological and instrumental tests were negative. Experts discovered reddish granules that would not even dissolve in reagents that dissolve blood, and one investigator found traces of what appeared to be paint. An art expert concluded that the image had been produced by an artistic printing technique. The commission's report was withheld until 1976 and then was largely suppressed, while a rebuttal report was made freely available.

Further examinations were conducted in 1978 by the Shroud of Turin Research Project (STURP). STURP was a group of mostly religious believers whose leaders s erved on the Executive Council of the Holy Shroud guild, a Catholic organisation that advocated the cause of the supposed relic.

STURP pathologist Robert Bucklin argued for the images anatomical correctness, yet a footprint on the cloth is inconsistent with the position of the leg to which it is attached, the hair falls as for a standing rather than recumbent figure, and the physique is so unnaturally elongated (similar to figures in Gothic art) that one pro-shroud pathologist concluded that Jesus must have suffered from Marfan's syndrome.

Famed microanalyst, Walter C. McCrone, examined 32 tape-lifted samples from the shroud and identified the 'blood' as tempera paint containing red ochre and vermilion along with traces of rose madder. These were the pigments used by medieval artists to depict blood. He also discovered on the image - but not the background - significant amounts of red ochre pigment. He first thought this was applied as a dry powder but later concluded that it was a component of dilute paint applied in the medieval grisaille (monochromatic) style. McCrone was held to a secrecy agreement, while statements were made to the press that there was no evidence of artistry. He says he was "drummed out" of STURP. Joe Nickell (Science and Religion: Are They Compatible?, Science Versus Shroud Science) says that STURP representatives paid a surprise visit to McCrone's lab to confiscate his samples, then gave them to two late additions to STURP, John Heller and Alan Adler, neither of whom was a forensic serologist or pigment expert. The pair soon proclaimed they had "identified the presence of blood".

The Shroud has also been carbon dated. Three laboratories were each given two samples of cloth, one from the shroud and one control sample. The results all stated that the linen was produced around 1250-1390 CE.

The Catholic Church seems unwilling to allow further tests at this stage, and further tests will in any case be as inconclusive as some claim existing tests have been, unless independence and transparency of the process are assured.

On this day in 1818:

The murderer Matthew Clydesdale was executed by hanging. His body was taken to the anatomy theatre at the Old College in High Street, where Dr Andrew Ure of Anderson's Institution and James Jeffray, Professor of Anatomy at the University, conducted a series of experiments using a galvanic battery, passing an electric current through the corpse. The resulting spasms and convulsions reportedly caused consternation among the attending students, and "several... were forced to leave the apartment from terror or sickness, and one gentleman fainted". The experiment gave rise to a persistent rumour that the professors had attempted to bring the corpse back to life.

This was one of the last occasions on which the corpse of an executed criminal was sent for dissection in Scotland.

• James Jeffray