A USA Today report has uncovered information that indicates federal marshals have secretly tracked almost 6,000 cellphones.
U.S. Marshals use powerful cellphone surveillance tools called stingrays to track suspects across the country.
Stingrays are mobile devices that look like cellphone towers and intercept cellphone signals.
Those towers are mounted to police cars.
Since cellphones are always seeking towers to connect to for signals, stingrays allow phones to connect to them and send data to it.
A connected laptop in the police vehicle displays the data for police to understand.
The data is then sent to a cellphone tower like normal.
Data includes numbers dialed by the cellphone, out going texts and calls, the number of the connected cellphone, and the location of the phone.
Cellphone users can not tell if their data has been sent to a stingray.
U.S. Marshals have used stingrays in 5,975 cases.
Compared to the NYPD, the number of times the U.S. Marshals have used stingrays is significantly higher.
The NYPD told the New York Civil Liberties Union that they used the devices over thousands of times since 2008.
The Baltimore Police Department, which has also controversially used the device, has used the technology over 4,300 times since 2007.
"That sheer number is significant,” American Civil Liberties Union lawyer Nathan Wessler said of the U.S. Marshal's number. “That’s a lot of deployments of a very invasive surveillance tool."
The agency would not name the suspects tracked, where they were arrested or the time period of the log, citing privacy.
The report said that the Marshals Service confirmed the use of stingrays by rejecting a request the new organization made under the Freedom of Information Act.
The request was for a log of instances in which the agency used stingrays.
A U.S. Marshals Service letter in response to the FOI request included a listing of stingray cases, described as "a listing of IMSI catcher use," but most of the information was censored line by line.
An IMSI catcher is another name for the stingray devices.
“For any sensitive technique, method, source or too, it only makes good sense that law enforcement would not divulge this information,” said William Sorukas, a former supervisor in the Marshal Service's domestic investigations division. . “An investigator would never release or publicize the name of a confidential informant.”
Marshal Service spokesman Drew Wade would not answer questions about stingray use. He only said that "various investigative techniques” are used to find fugitives and they are "subject to court approval."