What is facial recognition technology and why is it controversial?

Facial recognition technology is used worldwide. Credit: PA Images

The High Court is set to rule on the first legal challenge over police use of facial recognition technology in the UK.

Human rights campaigners backed the landmark court action after several police forces in England and Wales trialled the controversial technology.

Ed Bridges, from Cardiff, was represented by civil rights group Liberty at a three-day hearing in May as he challenged the use of automatic facial recognition (AFR) by South Wales Police.

Here's how facial recognition works - and why it is divisive.

  • How does it work?

It uses special cameras to scan the structure of faces in a crowd of people.

The system then creates a digital image and compares the result against a "watch list" made up of pictures of people who have been taken into police custody.

Not everybody on police watch lists are wanted for the purposes of arrest - they can include missing people and other persons of interest. If a match is found, officers in the area of the cameras are alerted.

  • How long has it been used?

South Wales Police piloted its technology during the week of the 2017 Champions League final in Cardiff, making it the first UK force to use it at a large sporting event.

  • Why is it controversial?

Campaigners say facial recognition breaches citizens' human rights. Liberty says scanning and storing biometric data "as we go about our lives is a gross violation of privacy".

Big Brother Watch says "the notion of live facial recognition turning citizens into walking ID cards is chilling". Some campaigners claim the technology will deter people from expressing views in public or going to peaceful protests.

It is also claimed that facial recognition can be unreliable, and is least accurate when it attempts to identify black people and women.

Before the hearing in May, Liberty said freedom of information requests had shown that South Wales Police's use of AFR "resulted in 'true matches' with less than 9% accuracy" in the first year.

  • What do the police say?

In May, South Wales Police barrister Jeremy Johnson QC told the High Court that AFR "potentially has great utility for the prevention of crime, the apprehension of offenders and the protection of the public".

He argued that there is "no difference in principle knowing you're on CCTV and someone looking at it, or that is being done automatically in a millisecond", adding that the images are deleted 24 hours later if there is no match.