By the early 1900s, fingerprints were competing with the Bertillon anthropometric system as the preferred method of criminal identification. A turning point came in 1903 with the notorious William West – Will West incident at Leavenworth Penitentiary in Kansas, USA. That year, a new inmate named Will West arrived at the prison, and routine Bertillon measurements (body dimensions) were taken. To the astonishment of prison officials, Will West’s measurements and physical description closely matched those of another prisoner already at Leavenworth – a man named William West.
According to accounts, the two men also bore a striking resemblance to each other. The staff initially suspected they might have the same person under two identities. Bertillon records alone could not definitively distinguish them – the system indicated a virtual duplicate.
However, the prison had recently begun using fingerprints. When fingerprint impressions of Will West and William West were compared, it immediately became clear that they were two different individuals, as their fingerprint patterns did not match at all. This revelation resolved the confusion and highlighted the superior reliability of fingerprints.
It was later speculated that the two men may have been identical twins, which would explain their similar anthropometric measurements – but even identical twins have different fingerprints.
The Will West case became a landmark example in the history of identification. Widely reported, it exposed the fallibility of Bertillonage and demonstrated how the older method could misidentify people. In contrast, fingerprinting provided conclusive differentiation.
As a result of this case, U.S. prisons and police departments hastened to adopt fingerprint identification. By 1904, Leavenworth prison began fingerprinting all incoming inmates, forming the beginning of a national fingerprint file. The Will/William West incident is often credited with ending the reign of the Bertillon system – after 1903, fingerprinting rapidly became the dominant method of criminal identification in America and beyond.

Comparison of Bertillon cards and fingerprints
Sources:
THE FINGERPRINT SOURCEBOOK