My understanding was it was fake government email accounts. Probably not encrypted or encrypted using a fake PKI token. If the message still exists somewhere, it’s likely the court can get the private and the public key.
Not sure what you mean by fake. There are two or more private keys involved. One for the sender so the sender can store an encrypted copy in the sent mailbox. Another for each recipient who uses it to decrypt the email which the sender encrypted with the recipient's public key (public keys are useless to a court). But most private keys are stored in the person's OS and have to be exported to a file to be given to a court. They can be marked as nonexportable when created in which case they cannot be given to a court.