A federal appeals court in Denver has ruled that e-mailed images obtained by the National Center for Missing and Exploited Children constituted a warrantless search and therefore must be suppressed as part of a child pornography case.

The 10th Circuit Court of Appeals ruled last Friday in favor of a Kansas man who sent an e-mail in April 2013 with four attachments that included suspected child porn via his AOL account. AOL immediately flagged the message via its hash value matching algorithm, believing one of the attached images was suspect, and sent them all on to NCMEC. (Providers have a "duty to report" to the NCMEC if their users access, transmit, or store child pornography.) The agency then opened his message and confirmed that Walter Ackerman had indeed attempted to transmit not just one, but four illegal images.

The following month, a Homeland Security Investigations special agent got the tip through the NCMEC system, and he sought and received a warrant to search Ackerman's home in Lebanon, Kansas. Under questioning, Ackerman admitted to distributing child pornography via e-mail. Months later, Ackerman was formally indicted on two counts of child pornography. His lawyers filed a motion to suppress in February 2014, arguing that his e-mail was searched illegally. Ackerman eventually accepted a plea deal in September 2014. Although he was sentenced to 170 months in prison, he was kept out of custody pending an appeal on the Fourth Amendment question.

Further Reading Court rules hash analysis is a Fourth Amendment “search”

NCMEC, which acts as the clearinghouse for suspected child sexual exploitation, occupies a sort of legal gray area. While the Alexandria, Virginia, entity is a Congress-created, publicly funded non-profit organization, it also takes on roles that are reminiscent of a law enforcement organization.

Indeed, the 10th Circuit wrestled with the question as to whether it was a “governmental entity or agent,” in which case it would be required to comply with Fourth Amendment standards and get a warrant to open a suspected e-mail. The appellate court found that NCMEC is, for all intents and purposes, a government agency, and even if it is not, it was still acting on the government’s behalf and thus had to abide by constitutional standards. In short, it needed to get a warrant to search Ackerman’s e-mail.

However, the case leaves open the possibility of an argument based upon the third-party doctrine, which holds that individuals do not have a privacy interest over their e-mail transmitted via a third-party (in this case, AOL). With respect to e-mail, only the 6th Circuit Court of Appeals has ruled that there is such a privacy interest and that the third-party doctrine does not apply. But the 6th Circuit ruling only applies in that district, which includes Kentucky, Michigan, Ohio, and Tennessee.

Prosecutors, who did not immediately respond to Ars’ request for comment, could re-raise this issue when the case gets sent back down to the federal district court in Kansas for further consideration.

When writing for the unanimous 10th Circuit, US Circuit Justice Neil Gorsuch concluded: