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Thursday, 20 August 2015

Writing – research – fingerprints-01

Beloved of crime novelists and readers, fingerprints have figured in fiction for a considerable time. They still have a part to play, even though we now have DNA profiling.

For hundreds of years, a thumb-mark was often used as a signature, but little was made of its uniqueness with regard to criminology.
Fingerprint - Wikipedia commons
The ‘papillary ridges’ we know as fingerprints are formed during the fourth and fifth months of the development of the foetus in the womb, and no changes occur after birth, save in size. No two individual fingerprints are believed to be alike (observed by JCA Mayer in 1788.)

In 1858, William Herschel, a young administrator of a rural area in Bengal, India, used right-hand first and middle finger prints of workers as signatures on contracts and receipts; then he extended the practice to all legal documents in his area and finally gave orders for prints to be taken of all convicted criminals so that identity would not be questioned. Twenty-one years later, he retired from the Indian Civil Service, taking his collection of fingerprints with him to England.

In Japan Henry Faulds, while working in the Scottish Medical Mission, became interested in fingerprints in pottery and experimented to such an extent that he discovered that fingerprints retained their uniqueness no matter how the hands were treated (with pumice stone, sandpaper, emery dust and even Spanish fly). He took prints of all ten digits. He wrote to the British scientific journal Nature in 1880, stating that ‘bloody fingerprints or impression on clay, glass etc’ could be used for the scientific identification of criminals.’ He named the technique dactylography.

His letter gained little interest, save that Herschel countered that his use of fingerprints antedated Faulds’. Dactylography remained unrecognised until after Fauld’s death.

However, Herschel gained the support of Sir Francis Galton who studied countless fingerprints and arrived at four distinguishing types:

Those with no delta (a small triangular area where the ridges ran together); those with a delta to the right; those with a delta to the left; those with several deltas.

He published his results in his book Finger Prints in 1892.

And in India yet again assistant magistrate Edward Henry studied Herschel’s techniques, even visiting London and Galton on leave.  By 1897, still in India, he developed a workable system of classifying the prints of all ten fingers, identifying arches, tented arches, radial loops, ulnar loops, and whorls, as well as deltas. The government of Bengal established the first national fingerprint bureau in the world.

In 1901 Henry was recalled from India and was appointed assistant commissioner of the Metropolitan Police, in charge of the Criminal Investigation Department (CID). He swiftly set up a Fingerprint Department.


Mark Sinden said...

To prove fingerprints are identical, there have to be a variable number of points of similarity (there's no clear standard - but it's generally in the region of 15-20). However, more recently it was established that it only takes ONE point that is clearly NOT identical to prove a fingerprint is NOT correct. There's also some doubt creeping in as to how reliable the whole process is, as with partial fingerprints a match may be found where a full fingerprint may give a difference. is worth a read.

Nik Morton said...

Thanks for the heads-up, Mark. (I used to be a subscriber to the Economist before emigrating to Spain! It seems to contain fair and incisive reporting). Fascinating item, thanks. Perhaps fingerprinting is better than witness reporting, but by how much? As pointed out, for serious cases (murder) one assumes that DNA is the prime measure of guilt...