For the first time, a federal judge has thrown out evidence obtained by police without a warrant using the controversial "Stingray" device that mimics cell phone towers to trick nearby devices into connecting with them, revealing private information.

U.S. District Judge William Pauley said the defendant's rights were violated when the U.S. Drug Enforcement Administration (DEA) used a Stingray to figure out his home address during a drug investigation.

Pauley rejected the evidence, writing, "The use of a cell-site simulator constitutes a Fourth Amendment search.... Absent a search warrant, the government may not turn a citizen's cell phone into a tracking device."
"This opinion strongly reinforces the strength of our constitutional privacy rights in the digital age."
—Nathan Freed Wessler, ACLU

The ACLU said it was the first time such a ruling has been issued and was a significant victory for privacy rights. The civil liberties group has long criticized the rampant secrecy surrounding Stingray use by law enforcement, estimating that at least 66 agencies in 24 states and the District of Columbia have the devices, but warning that the tally "dramatically underrepresents" actual use of Stingrays nationwide.

"After decades of secret and warrantless use of Stingray technology by federal law enforcement to track phones, a federal court has finally held the authorities to account," said Nathan Freed Wessler, staff attorney with the ACLU's Speech, Privacy, and Technology Project. "The feds are now firmly on notice that when they hide their intent to use invasive surveillance technology from courts and fail to get a warrant, their evidence will be suppressed. This opinion strongly reinforces the strength of our constitutional privacy rights in the digital age."

In March, a Maryland appeals court became the first appellate court to throw out Stingray evidence.

"We conclude that people have a reasonable expectation that their cell phones will not be used as real-time tracking devices by law enforcement, and—recognizing that the Fourth Amendment protects people and not simply areas—that people have an objectively reasonable expectation and privacy in real-time cell phone location information," the panel wrote at the time.