Eastern District holds that investigators violated 4th Amendment when they viewed suspected child pornography identified via “hash matching;” holds that good faith does not apply
United States of America v. Peter Braun, 24-CR-164 (E.D. Wis. 9/3/25).
In an interesting Fourth Amendment case, the Court holds that law enforcement violated Braun’s rights when it viewed suspected child pornography without a search warrant when that child pornography had not been previously viewed by an employee of an ESP.
Electronic service providers (ESPs), like Microsoft and Google, use “hash matching” to identify suspected child pornography hosted on their platforms. (p. 1). This process uses a computer algorithm that analyzes the underlying data comprising the electronic file. (Id.). Under federal law, ESPs must then report suspected child pornography to NCMEC, which, in turn, notifies law enforcement. (Id.). Sometimes, but not always, the ESP will have an employee “visually examine” the file to verify it is, in fact, child pornography. (p. 2). Other times, the ESP relies solely on the matching hash values. (Id.).
Here, NCMEC received multiple reports about suspected CP and the “reports all indicated the ESP had not viewed the contents of the uploaded files.” (Id.). The tips were linked to a single Wisconsin IP address. (Id.). As part of the ensuing law enforcement investigation, a special agent viewed the images and determined they were in fact CP. (Id.). After conducting additional investigation, including surveillance of the property, the agent applied for a search warrant. (p. 3). That warrant resulted in the discovery of contraband which Braun now argues should be suppressed. (Id).
Here, the general rule is that “police may repeat a search conducted by a private party so long as they do not exceed the scope of the earlier private search.” (p. 4). Thus, “In cases where a private party, such as an ESP employee, has visually examined the suspected child pornography file before passing it on to authorities, courts have held that the private search doctrine permits law enforcement to (also) view the image without obtaining a warrant.” (p. 6). Although the precise issue presented in this case has divided the federal circuits, the Court ultimately holds that “By viewing an image the ESP has not examined, a police officer clearly expands on the previous private search.” (p. 12). Accordingly, police were not permitted to “dispense with a warrant just because they are sure what they will find[.]” (p. 13).
Moreover, the Court rejects the Government’s argument that the search warrant established probable cause regardless of the agent’s visual verification simply because it referenced the hash matches. (Id.). Here, the Government omitted any discussion as to the reliability of hash matching in the warrant affidavit, a fatal flaw which undermines the existence of probable cause. (Id.).
Finally, the Government fails to prove that good faith excuses the decision not to obtain a warrant before visually inspecting the images. (p. 19). There was no binding appellate precedent specifically approving the practice and, even under a broader interpretation of the good faith doctrine, the law was sufficiently unsettled such that “officers should be encouraged to err on the side of obtaining a warrant, particularly where, as here, there is no exigency.” (p. 21).