George Washington University Law Professor Orin Kerr has published an article concerning privacy of computer data and the Fourth Amendment in the Yale Law Journal. Kerr details a test for determining when the copying of computer files constitutes a seizure under the Fourth Amendment. The introduction of “Fourth Amendment Seizures of Computer Data” (pdf) says:
Imagine the police take away a suspect’s computer, make a digital copy of its contents, and then give the computer back to the suspect. The police do not open the copy, but they keep it in their custody in case they need to access it later. Does the combined act of copying the files and retaining the copy trigger the Fourth Amendment?
Next imagine that FBI agents believe a particular person is using the Internet to commit a crime. Agents install a surveillance tool at the target’s Internet service provider (ISP), and the tool generates copies of all of the target’s incoming and outgoing email. The email is copied to a file, but no human being actually looks at the file. Instead, the agents keep the file in case they develop probable cause to look through it for evidence. Again, does the Fourth Amendment allow it?
The answer to both scenarios depends on whether copying computer files without looking at them constitutes a Fourth Amendment “seizure.” If copying a computer file amounts to a seizure, then the government cannot make and retain a copy absent special circumstances. On the other hand, if copying is not a seizure, then the government can make and retain the copy without restriction. The Fourth Amendment will limit looking through the copy because that is a Fourth Amendment “search.” But what if the government wants to make a copy and hold it? Does that constitute a “seizure”? […]
This Article attempts to solve the puzzle by offering a test for when copying data constitutes a Fourth Amendment seizure. It argues that copying data “seizes” it under the Fourth Amendment when copying occurs without human observation and interrupts the course of the data’s possession or transmission. It arrives at this definition by reaching back to the general purposes of regulating seizures in Fourth Amendment law and then applying those functions to the new environment of computers. The test it offers prevents the government from copying data without regulation, and yet also answers the objections that have puzzled scholars and made it difficult to apply the old definition of seizures in the new environment.
Under my approach, copying is neither never nor always a seizure. Whether copying amounts to a seizure depends both on whether it is pre-observation or post-observation and on whether it interrupts the intended transmission or use of the data. […]
Finally, this Article acknowledges a change in my own thinking. A few years ago, I argued that mere copying should not be considered a Fourth Amendment seizure. I acknowledged that copying ordinarily will be regulated by the Fourth Amendment. To my mind, however, copying was at most regulated by the restrictions on searches rather than seizures, and those restrictions were limited to copying that interfered with the operation of the machine from which the copy was made. I have now concluded that my prior approach was wrong. My earlier approach did not recognize the importance of access to data in the regulation of government evidence collection. Further, my earlier approach did not appreciate that a middle ground was possible to avoid some of the overbroad results that seem to follow from labeling copying a seizure. This Article identifies the new middle ground and explains why I now reject my earlier view.