Last week, EFF—along with the ACLU and EPIC—filed an amicus brief in the Wisconsin Supreme Court challenging a series of warrantless digital searches and seizures by state law enforcement officers: the search of a person’s entire cell phone, the retention of a copy of the data on the phone, and the subsequent search of the copy by a different law enforcement agency. Given the vast quantity of private information on an ordinary cell phone, the police’s actions in this case, State v. Burch, pose a serious threat to digital privacy, violating the Fourth Amendment’s core protection against “giving police officers unbridled discretion to rummage at will among a person’s private effects.”

The Facts

In June 2016, the Green Bay Police Department was investigating a hit-and-run accident and vehicle fire. Since Burch had previously driven the vehicle at issue, the police questioned him. Burch provided an alibi involving text messages with a friend who lived near the location of the incident. To corroborate his account, Burch agreed to an officer’s request to look at those text messages on his cell phone. But, despite initially only asking for the text messages, the police used a sophisticated mobile device forensic tool to copy the contents of the entire phone. Then about a week later, after reviewing the cell phone data, a Green Bay Police officer wrote a report that ruled Burch out as a suspect, finding that there was “no information to prove [Burch] was the one driving the [vehicle] during the [hit-and- run] accident.”

But that’s not where things end. Also in the summer of 2016, a separate Wisconsin police agency, the Brown County Sheriff’s Office, was investigating a homicide. And in August, Burch became a suspect in that case. In the course of that investigation, the Brown County Sheriff's Office learned that the Green Bay Police Department had kept the download of Burch’s cell phone and obtained a copy of it. The Brown County Sherriff’s Office then used information on the phone to charge Burch with the murder. 

Burch was ultimately convicted but argued that the evidence from his cell phone should have been suppressed on Fourth Amendment grounds. Last fall, a Wisconsin intermediate appellate court certified Burch’s Fourth Amendment challenge to the Wisconsin Supreme Court, writing that the “issues raise novel questions regarding the application of Fourth Amendment jurisprudence to the vast array of digital information contained in modern cell phones.” In December, the Wisconsin Supreme Court decided to review the case and asked the parties to address six specific questions related to the search and retention of the cell phone data.  

The Law

In a landmark ruling in Riley v. California , the U.S. Supreme Court established the general rule that police must get a warrant to search a cell phone. However, there are certain narrow exceptions to the warrant requirement, including when a person consents to the search of a device. While Burch did consent to a limited search of his phone, that did not provide law enforcement limitless authority to search and retain a copy of his entire phone.

Specifically, in our brief, we argue that the state committed multiple independent violations of Burch’s Fourth Amendment rights. First, since Burch only consented to the search of his text messages, it was unlawful for the Green Bay police to copy his entire phone. And even if his consent extended beyond his text messages, he did not give the police the authority to search information on his phone having nothing to do with the initial investigation. Next, regardless of the extent of  Burch’s consent, after the police determined Burch was no longer a suspect, the state lost virtually all justification in retaining Burch’s private information and should have returned it to him or purged it. Lastly, since the state had no compelling legal justification to hold Burch’s data after closing the initial investigation on him, the Brown County Sheriff’s warrantless search of the data retained by the Green Bay police was blatantly unlawful. 

The Privacy Threat at Stake

The police’s actions here are not an outlier. In a recent investigative report, Upturn found that law enforcement in all fifty states have access to the type of mobile forensic tools the police employed in this case. And although consent is a recognized exception to the rule that warrants are required for cell phone searches, Upturn’s study reveals that police rely on warrant exceptions like consent to use those tools at an alarming rate. For example, of the 1,583 cell phones on which the Harris County, Texas Sheriff’s Office performed extractive searches from August 2015 to July 2019, 53% were conducted without a warrant, including searches based on consent and search of phones the police classified as “abandoned/deceased.” Additionally, of the 497 cell phone extractions performed in Anoka County, Minnesota between 2017 to May 2019, 38% were consent searches. 

In light of both how common consent-based searches are and their problematic nature (as a recent EFF post explains), the implications of the state’s core argument is only all the more troubling. In the state’s view, no one—including suspects, witnesses, and victims—who consents to a search of their digital device in the context of one investigation could prevent law enforcement from storing a copy of their entire device in a database that could be mined years into the future, for any reason the government sees fit.

The state’s arguments would erase the hard-fought protections for digital data recognized in cases like Riley. The Wisconsin Supreme Court should recognize that consent does not authorize the full extraction, indefinite retention, and subsequent search of a person’s cell phone.