When the Founding Fathers wrote the Fourth Amendment in the eighteenth century, protecting a person's privacy meant forbidding unreasonable search and seizure of their "papers and effects." Today, in an age when messages, photographs, and even bank and credit card information are all available on a cell phone, that equation becomes a little more complicated. 

Civil rights activist Carol Rose, executive director of the Massachusetts ACLU, says that when it comes to protecting digital privacy, the laws just haven't kept up.

She points to a cell phone tracking technology used by police departments in 24 states, including Massachusetts. By imitating a cell phone tower, these trackers can download the information from all the cell phones in a surrounding area. 

But because the trackers harvest information based on physical proximity, not individual numbers, that means that the data from innocent bystanders can also get swept up.

"It's not just the person who might be a target, but all the people walking by whose phones might be downloaded," Rose said. "That creates legal issues."

It also means that law enforcement can collect a significant amount of data without first obtaining a probable cause warrant. In the state of Massachusetts, no law explicitly requires a warrant to be obtained before using this technology. But courts in states like Maryland and New York have thrown out evidence obtained with trackers.

In Massachusetts, a recent investigationfromthe New England Center for Investigative Reporting found that the Boston Police Department used cell phone tracking technology 11 times in a seven-year period without first obtaining a warrant, and also lent out the device to other departments. The Boston Police have declined to identify those departments, and it is unclear if warrants were obtained before the trackers were used.

On Boston Public Radio in February, Boston Police Commissioner William Evans said his department has only used trackers in emergency situations. Rose said the documents she has obtained from the department are too redacted to independently verify that claim.

"Of course, if there is a hostage situation or something, the ACLU doesn't say you have to get a warrant if there's an emergency situation," Rose said.

"In terms of what we've seen so far, our concern is just that, if you're going to have the technology, you're going to have to have rules and accountability," she continued.

To hear more from Carol Rose, tune in to Boston Public Radio above.