Millimeter-wave device at center of border weapon debate
The Pentagon has allowed the Department of Homeland Security to test the Active Denial System at the U.S.-Mexico border. The nonlethal device uses high-intensity 95-gigahertz millimeter waves for brief periods, penetrating about 0.4 millimeters into skin and heating water molecules to cause intense pain. Officials say the exposure is meant to be too short to damage tissue, but the weapon has rarely been deployed and remains controversial.
The Active Denial System was developed in the early 2000s and has seen scant operational use. It was reportedly tried briefly in Afghanistan in 2010; later, Los Angeles prison officials weighed riot-control testing but abandoned the idea after objections from civil-rights groups and the FCC.
Its practical limits include bulk and sensitivity to weather: rain, fog, or mist reduce the heating effect. Safety records are mixed—volunteer tests in 2005 and 2006 produced some blisters and rashes, and a 2007 misconfiguration caused second-degree burns to one airman—while researchers note little published data on such weapons.
If deployed, the device could affect migrants and border-area residents by introducing a painful, less-lethal option whose real-world safety is not well documented. Law-enforcement agencies may face questions about training, medical monitoring, and rules for use, while public trust could be shaped by how transparently any testing and incident reporting are handled. Its limited operational history may also leave policymakers and courts relying on incomplete evidence when weighing whether such a system is appropriate.