Brazilian police to use 'Robocop-style' glasses with facial recognition at World Cup
A small camera fitted to the glasses can capture 400 facial images per second and send them to a central computer database storing up to 13 million faces.
The system can compare biometric data at 46,000 points on a face and will immediately signal any matches to known criminals or people wanted by police.
If there is a match a red signal will appear on a small screen connected to the glasses, alerting the police officer of the need to take further action or make an arrest.
The devices will soon be tested at football matches and concerts and police in Brazil, South America's biggest country, are already planning to use them during the next World Cup.
The camera will generally be used to scan faces in crowds up to 50 metres (164ft) away but can be adjusted, if searching for a specific target, to recognise faces as far as 12 miles away.