In a big victory for privacy advocates and a blow to law enforcement, a D.C. federal judge ruled that authorities cannot track a suspect's cell phone without a warrant.

CBS News:

Law enforcement use of one tracking tool, the cell-site simulator, to track a suspect's phone without a warrant violates the Constitution, the D.C. Court of Appeals said Thursday in a landmark ruling for privacy and Fourth Amendment rights as they pertain to policing tactics.

The ruling could have broad implications for law enforcement's use of cell-site simulators, which local police and federal agencies can use to mimic a cell phone tower to the phone connect to the device instead of its regular network. 

In a decision that reversed the decision of the Superior Court of the District of Columbia and overturned the conviction of a robbery and sexual assault suspect, the D.C. Court of Appeals determined the use of the cell-site simulator "to locate a person through his or her cellphone invades the person's actual, legitimate and reasonable expectation of privacy in his or her location information and is a search." 

The Fourth Amendment guarantees, "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

D.C. Metropolitan Police's use of such cell-site simulator technology to nab suspect Prince Jones in 2013 "violated the Fourth Amendment," the court decided against the U.S. government on Thursday. 

"We thus conclude that under ordinary circumstances, the use of a cell-site simulator to locate a person through his or her cellphone invades the person's actual, legitimate and reasonable expectation of privacy in his or her location information and is a search," the court ruling said. "The government's argument to the contrary is unpersuasive."

A December 2016 report from the House Oversight and Government Reform Committee found U.S. taxpayers spent $95 million on 434 cell-site simulator devices between 2010 and 2014, with the price tag for a single device hovering around $500,000.

"While law enforcement agencies should be able to utilize technology as a tool to help officers be safe and accomplish their missions, absent proper oversight and safeguards, the domestic use of cell-site simulators may well infringe upon the constitutional rights of citizens to be free from unreasonable searches and seizures, as well as the right to free association," the report said.

These cell phone simulators cast a pretty wide net.  The simulators can gather huge amounts of information not related to the search for a suspect.  With that broad of a reach, it was only a matter of time before a court would rule these "stingray" searches unconstitutional without a warrant.

Police can still track a specific cell phone number in many cases without a warrant.  But the real-time ability of police to keep tabs on a suspect has been greatly reduced.

I think most of us are generally in favor of privacy rights, especially since there are so many snooping opportunities for authorities.  It remains to be seen how much this ruling will hamper the police in taking criminals off the streets.