Crucial oversight for Stingray investigations

Police are the good guys. They should use sophisticated technology to catch the bad guys. What they shouldn’t do is leave judges in the dark when they deploy spying technology of unprecedented power.

On at least 170 occasions in the last five years, investigators in Tacoma and nearby communities have asked Pierce County judges to approve warrants to track suspects with a futuristic device called a Stingray.

The problem: The judges knew nothing about the device. Nothing in the requests gave a hint of the device’s capabilities or even existence. In most cases, the judges probably assumed they were signing off on conventional methods for tracking phone calls.

The Tacoma Police Department, which owns the Stingray, did not want to reveal it to the public. The FBI, which provided it, was leaning on the city to keep the technology secret. As a result, the judiciary that monitors investigations for constitutional abuses wasn’t aware of the kind of surveillance it was authorizing. However noble the motives, this was subterfuge.

The furtiveness — reported by this newspaper in August — appears to be corrected. The 22 judges of the Pierce County Superior Court have now adopted an important safeguard: They insist that police disclose their intent to use the Stingray when they apply for “trap and trace” warrants.

Police don’t normally tell judges exactly how they intend to go about collecting phone data. There’s nothing particularly worrisome about traditional methods, such as ordering cell phone companies to disclose a suspect’s calls.

But a Stingray — which employs technology known as cell site simulation — is so much more intrusive than conventional surveillance that it demands extra scrutiny. It pulls in cellphone transmissions from all callers in a given area and identifies the unique signatures of each phone.

With that information, police can often determine a suspect’s precise location. Reportedly, it has been highly successful in nabbing criminals. Police ought to have this technology in their arsenals, provided it is used with respect for civil liberties.

But cell site simulation casts a very wide net. Though its reach is limited to small localities, it bears some resemblance to NSA data- mining. Because the devices pick up all cell phone signals, they could empower agencies to track the goings and comings of innocent bystanders. Some simulators — though apparently not the Stingray — can capture phone conversations.

This could get spooky in a hurry. The Pierce County Superior Court now has another safeguard in place: Police must sign affidavits that they will not store data on people who are not targets of the investigation.

Cell site simulation is on the frontier of law enforcement technology. Not surprisingly, it’s also on the frontier of the law itself. The courts haven’t had a chance to clearly define its constitutional limits and legitimate uses.

That raises the possibility that criminal convictions may someday be overturned if investigators overstep boundaries — including boundaries that haven’t been drawn yet and won’t be until cases reach courts of appeals.

Defense attorneys may well succeed at freeing convicts from prison in cases where police didn’t use the technology cautiously. That’s reason enough to keep judges informed when these machines are part of the investigation.