CBA Record January-February 2026

include intercepting private phone conversations (Katz v. United States) ; thermal imaging to detect activity inside the home (Kyllo v. United States) ; GPS tracking of a vehicle’s movement (United States v. Jones) ; and cell-site location data from a phone carrier (Carpenter v. United States). Search Warrants and Smart Phones In Riley v. California , the Supreme Court held that police must obtain a warrant before searching a cell phone. Before Riley, the police could search anything that a suspect carried on their person when they were arrested (known as a “search incident to arrest”) without a warrant. By the time of that 2014 decision, it was clear that smartphones were different from anything else that you carry in your pocket. In his opinion for the Court, Chief Justice Roberts emphasized that: “Modern cell phones are not just another technological con venience. With all they contain and all they may reveal, they hold for many Americans ‘the privacies of life.’” Since the Riley case, law enforcement officers around the coun try have obtained search warrants for countless smartphones. In the search warrant application, the officer must explain to a judge why they believe the phone contains evidence of criminal activity. The application must also specify the items the officer is searching for. For instances, in a carjacking investigation, the officer may be looking for messages and photos related to cars and guns, and location data from the times of the carjackings. If the judge signs the warrant, the officer can extract an image of the phone’s contents—essentially making a copy of a digital file. So long as the cell phone does not contain contraband (such as child pornography), the officer will return the cell phone, unaltered, to the suspect. The officer then searches the digital extraction of the cell phone’s contents, rather than the cell phone itself. After reviewing the phone for the items in the list, the offi cer makes a separate copy of that evidence, which they put in the case file. The full contents of the phone cannot be searched again. This process ensures that our “privacies of life” cannot be re-opened indefinitely. AI assistants cannot be searched like smartphones because they maintain information in a way that will be indecipherable to an officer. Just like you maintain memories of events based on what you saw, heard, read, or where you were, so too will the AI assistant. To learn what the user was doing, law enforcement will have to prompt the device with questions. AI assistant developers will design devices to respond only to the owner—for example, through facial or voice recognition, passcodes, or fingerprints. But law enforcement will inevitably find ways to break through those protections, just as they do now with software that breaks cell phone passcode protection. This will lead to the philosophical and legal question: Will Why the Search of AI Assistants is Fundamentally Different

prompting of a suspect’s AI assistant divulge the contents of the mind? Some may argue that querying an AI assistant to reconstruct events is no different from compelling access to an encrypted device: The user’s historical information exists in an altered form, and the AI assistant simply retrieves and makes sense of it. Under this view, a prompt to an AI assistant does not invade the user’s mind any more than a key to their file cabinet. But this analogy does not hold up. Files in a locked cabinet exist before they are found. So do encrypted messages. By con trast, by prompting an AI assistant, law enforcement will be gen erating new content. Even today, you can ask ChatGPT the same

While the Fifth Amendment provides useful background on mental privacy, the Fourth Amend ment is better suited to protect the privacy of the mind.

question on different days and get different answers. They are dynamic systems. And when they become integrated with your mind, they will become far more dynamic. AI assistants may someday become physically connected to your brain. With the emergence of brain-computer interfaces (such as Neurolink) and nanotechnology (microscopic devices capable of interacting with neural tissue), AI may soon receive direct neural input from the user’s brain. In other words, AI assis tants will become a physical extension of the user’s mind. At that point, courts may view prompting of the AI assistant as a digital interrogation of the user themselves, even if the AI assistant is physically disconnected from the user at the time of the search. But should constitutional protection hinge on whether the AI assistant is physically connected to the brain? AI assistants will be revealing our most private thoughts long before that point. The Fourth Amendment has a long track record of evolving with technology. It is also more flexible than the Fifth because it has more exceptions to the exclusionary rule. For example, the Fourth Amendment allows the police to search without a war rant in emergencies (“exigent circumstances”) such as the “tick ing timebomb” scenario. Because guarding mental privacy is so dependent on rapid changes in technology, courts should look to procedural rules under the Fourth Amendment rather than categorical line-drawing under the Fifth. Policing Mental Privacy with the Fourth Amendment, not the Fifth

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