On June 19, 1892, Argentinian mother of two Francisca Rojas became the first criminal in the world to be found guilty through fingerprint evidence.
Rojas, 27, murdered her two children at their home in Necochea, Buenos Aires Providence. Her six-year-old son, Ponciano Carballo Rojas, and his four-year-old sister Teresa were found brutally murdered.
Francisca tried to frame her neighbor Pedro Ramon Velázquez, who had reportedly been courting her, by cutting her own throat and then blaming him. But even after torturing Velázquez, including by tying him to the children’s corpses overnight, the police could not get him to confess.
After the report of the murder reached La Plata on July 8, Police Inspector Alvarez of the Central Police was sent to Necochea to assist local police with the investigation. When he arrived, he found the police investigation had hit a dead end.
Rojas and Velázquez still both denied killing the children.
Alvarez quickly determined that Velázquez had an alibi, having been out with several friends at the time of the murders. Alvarez also learned that Rojas’ other boyfriend had been overheard saying he would marry her “except for those two brats.”
While examining the scene, Alvarez discovered a brown mark on a bedroom door that he later determined to be a bloody fingerprint. Investigators contacted Juan Vucetich, who was in charge of criminal identification and was developing a system of fingerprint identification for police use.
Remembering the training he received from Vucetich, Alvarez removed the section of the door with the impression — and then then requested Rojas be fingerprinted for evidence. Vucetich compared the fingerprints of Rojas and Velázquez with the bloody fingerprint and, although Rojas had denied touching the bloody bodies, the fingerprint matched one of hers. When police confronted her, Rojas confessed to the murders, and was convicted.
Crucially, the case laid the groundwork in proving the superiority of fingerprints for personal identification purposes as compared to anthropometry, which is form of identification based on taking measurements from 11 different areas of the human body.
As a result of the Rojas murders, Argentina became the first country in the world to abolish anthropometry and file its criminal records based solely on fingerprint classification. The resulting classification system is still used in many South American countries today.