The New York Civil Liberties Union believes that the New York City Police Department used Z Backscatter Vans (aka X-ray vans) when surveilling certain neighborhoods.

The NYCLU filed a motion for leave to file an amicus brief urging the Appellate Division, First Department to uphold a lower court’s decision requiring the NYPD to release information the use of these X-ray vans.

According to the NYCLU, the Brennan Center for Justice joined them on the motion and brief.

This brand of military-grade surveillance equipment was used to search for roadside bombs in Afghanistan. The instrument uses X-ray radiation to image the inside of cars and buildings. NYPD officials initially denied a Freedom of Information Law request by a ProPublica journalist asking for records about the public health risks, the prior use of the vans and if the department is using them. With the force allegedly paying $729,000 and $825,000 for the two vans used, the NYPD hasn’t revealed how much it actually spent on the two units.

“People should be informed if military-grade X-ray vans are damaging their health with radiation or peering inside their homes or cars,” said NYCLU Executive Director Donna Lieberman in a statement. “New Yorkers have a right to protect their health, welfare and privacy.”

“Fair policing requires the NYPD to be willing to tell New Yorkers when it is using technologies that significantly intrude on their privacy,” added NYCLU Senior Staff Attorney Mariko Hirose in a statement. “The NYPD is out of step with the growing recognition that public awareness of how law enforcement conducts surveillance is important for democracy.”

The NYPD claimed, in court, that disclosing any information regarding the X-ray vans would compromise ongoing investigations, but the court found that police officials didn’t show how disclosing any information would ruin said investigations. Lieberman and the rest of the NYCLU also noted that other agencies, such as the Department of Homeland Security, have revealed similar information about the same type of technology before.