Thickness compass (Compas d'epaisseur) for the measurement of the length and breadth of the head in Bertillon's anthropometrical criminal identification system, perhaps Bertillon's own, from the Paris Prefecture of Police, c. 1883

The Préfecture de Police in Paris used this thickness compass as part of the Bertillon criminal identification system. It measured the length and breadth of the head. French criminologist Alphonse Bertillon (1853 –1914) developed an identification system called anthropometrics. This recorded detailed physical measurements to identify individuals. Bertillon used the thickness compass and other tools to measure height, head circumference, arm length, leg length, finger lengths and eyeball protrusion. His system was used to identify suspects in criminal cases. The system was extremely popular in France, leading to many convictions. It was superseded by more accurate and less labour-intensive fingerprinting. Bertillon pioneered many modern forensics techniques such as the ‘mug shot’, which is the standardised photography of criminals.