The Government Shouldn’t Prosecute People With Unreliable “Black Box” Technology

On Tuesday, EFF urged the Massachusetts Supreme Judicial Court, the highest court in that state, to affirm that a witness who has no knowledge of the proprietary algorithm used in black box technology is not qualified to testify to its reliability. We filed this amicus brief in Commonwealth v. Arrington together with the American Civil Liberties Union, the American Civil Liberties Union of Massachusetts, the National Association of Criminal Defense Lawyers, and the Massachusetts Association of Criminal Defense Lawyers. 

At issue is the iPhone’s “frequent location history” (FLH), a location estimate generated by Apple’s proprietary algorithm that has never been used in Massachusetts courts before. Generally, for information generated by a new technology to be used as evidence in a case, there must be a finding that the technology is sufficiently reliable.  

In this case, the government presented a witness who had only looked at 23 mobile devices, and there was no indication that any of them involved FLH. The witness also stated he had no idea how the FLH algorithm worked, and he had no access to Apple’s proprietary technology. The lower court correctly found that this witness was not qualified to testify on the reliability of FLH, and that the government had failed to demonstrate FLH had met the standard to be used as evidence against the defendant. 

The Massachusetts Supreme Judicial Court should affirm this ruling. Courts serve a “gatekeeper” function by determining the type of evidence that can appear before a jury at trial. Only evidence that is sufficiently reliable to be relevant should be admissible. If the government wants to present information that is derived from new technology, they need to prove that it’s reliable. When they can’t, courts shouldn’t let them use the output of black box tech to prosecute you. 

The use of these tools raises many concerns, including defendants’ constitutional rights to access the evidence against them, as well as the reliability of the underlying technology in the first place. As we’ve repeatedly pointed out before, many new technologies sought to be used by prosecutors have been plagued with serious flaws. These flaws can especially disadvantage members of marginalized communities. Robust standards for technology used in criminal cases are necessary, as they can result in decades of imprisonment—or even the death penalty. 

EFF continues to fight against governmental use of secret software and opaque technology in criminal cases. We hope that the Supreme Judicial Court will follow other jurisdictions in upholding requirements that favor disclosure and access to information regarding proprietary technology used in the criminal justice system.   

• EFF Amicus Brief in Commonwealth v. Arrington