A “pain ray” that Los Angeles County sheriff’s officials want to use in a Castaic jail has drawn heat from the American Civil Liberties Union, which said Thursday the device could severely injure inmates.

The Assault Intervention Device is considered a non-lethal device and is intended to break up prison riots quickly. The ACLU, however, begged to differ in a letter to sent Thursday to Sheriff Leroy Baca. 

“We strongly oppose the view that it is ever appropriate to deploy against the detainees of a county jail — or any incarcerated population — a military weapon intended to cause intolerable pain and capable of causing severe injury or death,” the letter reads, saying a more powerful version of the device being tested by the Air Force burned five airmen.

Peter Eliasberg, the managing attorney for the ACLU of Southern California, said calling a device “non-lethal” could wrongly convince deputies the weapon presents no risk to inmates. 

“Deputies know the benefits and real risk of batons and guns,” Eliasberg said. “But when we advertise these weapons as miracle devices, they give (deputies) a false sense of security and they do get overused.”

But sheriff’s officials said the device will prevent violence by allowing a single deputy to break up fights quickly. Currently, deputies will use batons, pepper spray, Tasers and rubber-ball grenades, which can cause greater injury than the device, said Commander Bob Osborne.

“I think it will prove to be a very effective tool to prevent injuries on deputies and other inmates,” Osborne said. “If I didn’t believe that with all my being, I wouldn’t try it.”

Sheriff’s department officials unveiled the Assault Intervention Device at a press conference Friday at Pitchess Detention Center’s North County Correctional Facility. Officials plan to install the device in a jail dormitory in the next several months.

Two days later, more than 200 inmates at the Pitchess Detention Center’s South Facility armed themselves with shanks and threw rocks at deputies in a coordinated attack Sunday afternoon. The incident lasted about two hours and left several inmates injured.

The device, which was developed by Raytheon Company, shoots a millimeter wave about 75 feet that causes an intolerable burning sensation. The waves penetrate a person’s skin and agitate his or her pain receptors.

At the press conference, Raytheon officials said the device doesn’t cause injuries.

Osborne said the sheriff’s department has been working with the United States Department of Justice since March 2008 to bring the device to Pitchess and it will be tested at the prison for six months.