For the past 15 years, police forces searching for criminals in Europe have been able to share fingerprints, DNA data, and details of vehicle owners with each other. If officials in France suspect someone they are looking for is in Spain, they can ask Spanish authorities to check fingerprints against their database. Now European lawmakers are set to include millions of photos of people's faces in this system—and allow facial recognition to be used on an unprecedented scale.

The expansion of facial recognition across Europe is included in wider plans to "modernize" policing across the continent, and it comes under the Prüm II data-sharing proposals. The details were first announced in December, but criticism from European data regulators has gotten louder in recent weeks, as the full impact of the plans have been understood.