Senators Edward J. Markey, Ron Wyden and Jeff Merkley sent a letter Thursday to Acting US Immigration and Customs Enforcement (ICE) Director Todd Lyons urging the agency to stop using “Mobile Fortify,” a smartphone app that uses biometric identification, including facial recognition. The lawmakers said facial recognition remains unreliable and warned that real-time surveillance could have a chilling effect on constitutionally protected activities.

"As studies have shown, when individuals believe they are being surveilled, they are less likely to engage in First Amendment-protected activities, such as protests or rallies — undermining the very core of our democracy,” the senators wrote.

They requested answers from the agency by October 2 as to who built the app, when it was deployed, whether ICE tested its accuracy, the legal basis for its use and current agency policies governing the tool’s use. They also asked whether ICE would commit to ending the use of Mobile Fortify, and to explain why if they would not. The letter was also signed by Senators Elizabeth Warren, Cory Booker, Chris Van Holle, Tina Smith, Bernie Sanders and Adam Schiff.