Wimer

I. FACTUAL AND PROCEDURAL BACKGROUND

A. The Prosecution Case In April and May 2017, Sergeant Christopher Servat of the San Francisco Police Department used an investigative software program to search the BitTorrent network for suspects distributing child pornography. As Sergeant Servat explained, BitTorrent is a peer-to-peer file sharing network that “is used to share, download, [and] distribute” “massive amounts of data” over the Internet, such as movies, videos, and music. The network is also used to distribute child pornography. To download and share files over a BitTorrent network, a user must install a BitTorrent software client on his or her computer and download a “torrent” from a torrent-search website. A torrent contains information about the target files, including their names, sizes, and cryptographic “hash values,” which are the numeric codes assigned to a file and considered “the DNA of a file.” The software client reads the torrent, finds the pieces of the target file from other BitTorrent users who have the same torrent, and downloads and assembles the pieces, producing a complete file. Law enforcement officers have identified many hash values that are…