Thanks to this call-and-response process, the Stingray knows both what cell phones are in the area and where they are. In other words, it gathers information not only about a specific suspect, but any bystanders in the area as well. While the police may indeed use this technology to pinpoint a suspect’s location, by casting such a wide net there is also the potential for many kinds of constitutional abuses—for instance, sweeping up the identities of every person attending a demonstration or a political meeting. Some Stingrays are capable of collecting not only cell phone ID numbers but also numbers those phones have dialed and even phone conversations. In other words, the Stingray is a technology that potentially opens the door for law enforcement to sweep up information that not so long ago wouldn’t have been available to them.
This is why it matters who wins the mayor and city council races. Localities do not have to accept this technology.
You see but you do not observe. Sir Arthur Conan Doyle, in "The Memoirs of Sherlock Holmes"