... the appeals court, like the police, agreed that the presence of child porn on his drives was a "foregone conclusion." The Fifth Amendment, at its most basic level, protects suspects from being forced to disclose incriminating evidence. In this instance, however, the authorities said they already know there's child porn on the drives, so Rawls' constitutional rights aren't compromised.
The Philadelphia-based appeals court ruled:
Forensic examination also disclosed that Doe [Rawls] had downloaded thousands of files known by their "hash" values to be child pornography. The files, however, were not on the Mac Pro, but instead had been stored on the encrypted external hard drives. Accordingly, the files themselves could not be accessed.
The court also noted that the authorities "found [on the Mac Book Pro] one image depicting a pubescent girl in a sexually suggestive position and logs that suggested the user had visited groups with titles common in child exploitation." They also said the man's sister had "reported" that her brother showed him hundreds of pictures and videos of child pornography. All of this, according to the appeals court, meant that the lower court lawfully ordered Rawls to unlock the drives.