In the late 1800s, police departments around the world faced a problem; while they could often pin a crime on a specific individual and arrest them, they could not reliably tell if a person was a repeat offender. By simply using an alias (and perhaps changing towns frequently) a criminal could plead that this was a first offence, potentially getting off with a lighter sentence1.
Alphonse Bertillon made a number of advancements in the field of criminal forensics, but he is perhaps best known for his personal identification system -- the Bertillon system of criminal identification, commonly shortened to Bertillonage. This was a simple anthropometric system -- that is, a system based on physical measurements of body parts -- that had a high statistical probability of providing a unique identifier for a given individual.
Bertillon noted that after the age of 20, the bone structure of the individual was largely fixed. While any given measurement would be common throughout a population, taken in conjunction a set of eleven different measurements would provide an essentially unique identifier. These were measurements of the head and face, of height, and the hands and arms, but were used in conjunction with the usual physical descriptions of hair and eye color, birthmarks, and other identifying features.
This system was formalized by Bertillon in 1879, and was in use by the French police force within a few years. It was supplemented in 1888 by Bertillon's standardization and implementation of the mug shot system2. In short order Bertillonage came to be used around the world; it was a quick and easy way to share identifying information between jurisdictions, and many precincts had a Bertillon cabinet, much akin to a library's card catalog, with cards organized by head size.
In 1892 Juan Vucetich set up the first fingerprint bureau in Argentina, and both Bertillonage and fingerprinting were used in many precincts. However, in 1903 an American case of unrelated but eerily similar criminals, commonly referred to as the West Brothers3 case, proved that fingerprinting could identify people even in cases where Bertillonage could not. Moreover, proper Bertillonage required the use of a specifically trained 'Bertillon operator', who would take proper care in making the exacting measurements; in some precincts this operator was not as trained and careful as one might hope.
The Bertillon system continued to be used for decades, although it was no longer the gold standard it once was. Bertillonage was still useful in that it could be completed fairly easily and without eyestrain, and that data could easily be communicated over telegraph
; however, when it came to bringing a criminal to court, fingerprints ruled over mugshots and Bertillon measurements.
1. At this time, in France, the law allowed for rehabilitation for first offenders, but much harsher sentences for repeat offenders. Meanwhile, in Britain, the Habitual Criminals Act of 1869 allowed for reoffenders to be subject to police supervision for seven years to ensure that they were making an honest living.
2. Bertillon standardized the format of the mugshot system, but more importantly tied it into his filing system. Previously, mugshots might be taken from any distance or angle, and would be filed by name only. His system filed the mugshots with the anthropometric data, so that a criminal could not simply lie about their name and thus count on their mugshot being lost in the morass of the filing system.
3. In 1903 a man named Will West was committed to the penitentiary at Leavenworth, Kansas. His measurements were found to be almost identical to a criminal at the same penitentiary named William West, who had been arrested for murder in 1901, and was currently serving a life sentence. Their mugshots also showed a very close physical resemblance. There is no evidence that they were related, the brotherhood, in this case, being a rhetorical flourish on the part of later writers.