Heat Ray on Mexico Border: US Weapon Raises Safety Concerns

US Defense Secretary Pete Hegseth agreed to lend the Active Denial System, known as the heat ray weapon, to the Department of Homeland Security for seven months to test it and study its potential use along the US-Mexico border, according to CNN.

The weapon uses invisible beams of electromagnetic energy to cause an intense burning sensation on human skin, raising questions about safety and legal aspects of using military technology against migrants, particularly regarding the possibility of causing injuries or endangering people attempting to cross the border.

Allowing the weapon to be tested does not necessarily mean a decision has been made to deploy it, as it remains unclear whether the Department of Homeland Security will actually use it on the border.

A spokesperson for Customs and Border Protection said the agency continuously evaluates new technologies, especially those that can contribute to saving lives and enhancing national security effectiveness.

For his part, Patrick Weaver, Hegseth's deputy chief of staff, said in a post on the X platform that the border has become a military facility and field laboratory for testing new systems, including directed-energy weapons.

How does the heat ray weapon work?
The Active Denial System has a range of up to 1000 meters and emits an invisible beam of electromagnetic energy that penetrates the skin to a depth of about 1/64 of an inch, rapidly heating its surface and causing an intense burning sensation, according to the US Department of Defense.

Officials compare this sensation to the heat felt when opening a hot oven, explaining that its intensity triggers an almost immediate reaction to move away from the beam.

The burning sensation stops when the person moves out of the energy path, but tingling or sensitivity may last for 10 to 15 minutes, according to the Pentagon.

The US Department of Defense states that the system is designed to be non-lethal, clarifying that killing someone with it would require prolonged exposure to the beam several times longer than the duration needed to force them to move away.

However, the weapon caused second-degree burns in at least two documented incidents. In a 1999 incident inside a laboratory, one person suffered a blister, while an Air Force member sustained burns during training in 2007 due to procedural errors leading to excessive radiation exposure. The soldier fully recovered from his injury.

The Pentagon notes that operating procedures, controls, checklists, software updates, and training help reduce the risk of injury.

Previous attempts to use technology on the border
The idea of using directed-energy weapons on the US border is not new. The US Air Force began researching this technology in the late 1980s, while the Pentagon developed the Active Denial System as part of a military pilot project between 2002 and 2007.

CNN reported that former Homeland Security Secretary Kirstjen Nielsen rejected a proposal in 2018 to use this technology against migrants.

In July 2025, the Pentagon's Joint Capability Office for Medium Forces published an article advocating for the use of energy weapons, including active denial technology, to enhance border security.

Ethical and legal concerns
The weapon has raised ethical and legal questions since its development due to its design to inflict pain on those exposed to it.

Jared Keller, author of the defense technology newsletter "Laser Wars," said the appropriateness of using the weapon on the southern border depends on how its effects are interpreted, adding that he does not support its use there.

Keller considered the step further evidence of the transformation of the US border into a field laboratory for testing new technologies. He pointed to the use of high-power lasers, small drones, and futuristic heads-up displays as examples of technology being tested in this context.