After a relaxing weekend away, Guillermo Ibarrola was walking out of a train station in Argentina's capital when police arrested him and accused him of a robbery committed hundreds of miles away in a place he had never visited. "It was a nightmare," Ibarrola told local media after the 2019 incident, which rights campaigners say highlights the risks of using facial recognition systems to survey populations. The system of 300 cameras linked to a national crime database -- dubbed Buenos Aires' Big Brother -- was suspended two years ago after a court found it may have been used to collect data on journalists, politicians and human rights activists, and ruled it unconstitutional.

This story was made possible with support from the Pulitzer Center's AI Accountability Network. "And then the nightmare began," says Guillermo Ibarrola, recalling his arrest at the crowded train station in the city center of Buenos Aires where we stand. He points to the cameras at the end of the tracks, then his finger pans to a door at the edge of the large station hall of the heritage-listed building. "That's where they kept me for six days." He slept on bare concrete, in a small cell.

In July 2019, Guillermo Federico Ibarrola was heading home on the subway when he was stopped by Buenos Aires police. The authorities told Ibarrola that he was being detained for an armed robbery that had happened three years ago in a city about 400 miles away. He said he had never even been to the city where he was accused of committing the crime. On the sixth day in police custody, he was suddenly released. The police officers offered Ibarrola coffee and dinner, and a bus ticket back home. As it turned out, a "Guillermo Ibarrola" had potentially committed a crime, but it wasn't this Guillermo Ibarrola.