A big question in law is how much privacy a person should have in their cell phone. Smartphones are complex tools that allow a person to connect with people and places all over the world. Often we know how we are connecting. We send a text, an email, a video, or post on social media. However, sometimes we might not be aware that we are connecting with others, like when we connect to cell phone towers to get service.
The highest court in Massachusetts recently decided a case on “tower dumps” and how police use the connections we are not always aware of to solve crimes. The case helps us better understand how much privacy we have when we use a smartphone.
How do cell phone towers work?
The case decided by the Massachusetts Supreme Judicial Court is called Commonwealth v. Perry and it is all about cell phone towers. To understand it, we have to first understand how the technology involved works.
To make a call, send a text or email, or access the internet, a smartphone must connect to a set of radio antennas called a cell site. Phones do this automatically and typically go for the cell site providing the strongest signal. This is usually the tower closest to the cell phone. Cell sites cover a circular area around the tower. The circular coverage area is divided into wedge-shaped slices called sectors.
When a cell phone connects with a cell site, the cell site generates a time-stamped record called a cell site location information (CSLI) point. Each data point records which cell site tower the phone connected to and within which sector of the cell site the phone connected to. Since phones are frequently connecting or “pinging” cell sites, analyzing a large collection of CSLI data can create a kind of map tracing a person’s movements.
What happened in the Perry case?
From September to October 2018, an unidentified perpetrator and an accomplice robbed seven convenience stores and gas stations in Boston, Canton, and Cambridge. During one of the robberies, the store clerk was shot and killed. Witnesses described the perpetrator in a similar way, leading police to suspect that the same person committed each crime.
To track down the perpetrator, police decided to analyze data from several tower dumps. A tower dump is an electronic file containing the CSLI for all the devices that connected to a cell site tower during a certain period. Police believed that if they analyzed the data within several tower dumps near the locations of the robberies, they would be able to determine if any phone was near the scenes of more than one of the robberies.
To get the data, police applied for search warrants. The search warrants were presented to the phone companies who owned it and police obtained a large quantity of CSLI. The information revealed over 50,000 telephone numbers that had pinged to the towers during the about two-month period the robberies took place.
Police investigators then analyzed the data and were able to connect one phone number corresponding to the homicide-robbery and another robbery in October. This was traced to the defendant in this case, Jerron Perry. From this information, police deduced that Mr. Perry’s phone was communicating with another phone number suspected to belong to the accomplice, who was the getaway driver. The suspected getaway driver’s phone number was also reported to have pinged to the cell site towers.
Based on all this, prosecutors filed criminal charges against Mr. Perry.
What was the legal issue in the case?
The main legal issue in the Perry case was this: Was it lawful for police to get access to so much CSLI data from the phone companies?
The constitutions of the United States and Massachusetts say that people have a right to be free from unreasonable searches. To determine if this right was violated, the legal analysis has two parts:
- First, was there a search?
- Second, was the search reasonable?
In other words, if there was no search, it does not matter if the search was unreasonable. Importantly, when we are talking about searches they have a very specific legal definition. In Massachusetts, a search means that the government has intruded on a person’s reasonable expectation of privacy.
The Court analyzed the case exactly this way. The first question was if Mr. Perry was searched. In other words, did he have a reasonable expectation of privacy in his phone’s CSLI data? If he did not, what the police did was lawful. If he did, the next question was if the search of his CSLI data was reasonable. If it was reasonable, police did not violate the law. If it was not reasonable, police did and the fact that police used the CSLI to track Mr. Perry’s number and the suspected accomplice’s number could not be used against him during his trial.
Does a person have a reasonable expectation of privacy in their CSLI?
The Court began its discussion of the law by evaluating if Mr. Perry had a reasonable expectation of privacy in his CSLI. The Court used a legal idea called the mosaic theory. In Massachusetts, a person is searched when government surveillance is so sweeping that the data it collects reveals all together something private about a person’s life. In other words, all the individual data points together reveal something unknown about the person targeted, like how all the small stones in a mosaic create a bigger picture.
To determine if the CSLI created a “mosaic” of Mr. Perry’s life, the Court said we should look at these factors:
- How much the surveillance reveals about the target’s movements
- The type of information obtained
- If the surveillance could have been conducted using tradition law enforcement methods, like stakeouts and tailing suspects
The Court analyzed these factors one by one and concluded that the tower dumps intruded on Mr. Perry’s reasonable expectation of privacy. This meant that the answer to the first question was yes: Mr. Perry was searched.
The Court said that the CSLI viewed all together revealed very personal and private information about Mr. Perry. This information revealed so much that police were able to identify who he was, where he had traveled to, and who he interacted with. Because of how hard it would have been to follow every one of Mr. Perry’s movements, traditional surveillance methods would not have worked. In fact, police never would have followed Mr. Perry before he was a suspect.
Was the search of Mr. Perry reasonable?
Once it concluded that Mr. Perry was searched because his reasonable expectation of privacy was violated, the Court turned to if the search was reasonable.
Police do not always need a warrant to search a person but often they get one. When police have a search warrant, a search is usually reasonable. It is not reasonable when any of the following is true:
- There is no probable cause, or reason to believe the thing police want to search contains evidence of a crime or contraband, like an illegal weapon or drugs
- There is something wrong with the warrant itself and the sworn statement that is a part of it, called the affidavit
- For example, the warrant is not specific or particular enough about what police want to search
In a very lengthy analysis, the Court separately analyzed each of the two search warrants police obtained. It concluded that the second warrant met all the legal requirements but that the first was bad because there was no probable cause. Because of this, only the CSLI police obtained from the second warrant could be used against Mr. Perry.
Why is this case important?
The Perry case is important for many reasons. The most important reason is that it shows that people have privacy rights in their smartphones. Even though by using your phone you are automatically sending data about your location to phone companies, you still have a reasonable expectation of privacy in your data all together, or in the aggregate.
The case is also one of many reminding that the government has to meet certain legal requirements to search someone. All searches must be reasonable. This means the police cannot search you unless they have reasons that hold up in court. An effective criminal defense attorney will ensure that your legal rights are protected by carefully reviewing any warrants police take out to access your data.
IF YOU OR A LOVED ONE HAVE BEEN CHARGED WITH A CRIME AFTER POLICE SEARCHED YOUR PHONE, AND YOU NEED AN EXPERIENCED CRIMINAL DEFENSE LAWYER WORKING ON YOUR SIDE TO PROTECT YOUR RIGHTS, PLEASE CONTACT CRIMINAL DEFENSE ATTORNEY WILLIAM J. BARABINO.
CALL 781-393-5900 TO LEARN MORE ABOUT YOUR AVAILABLE DEFENSES.
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