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.
Sorry, I should say the sender’s private key is so the sender can decrypt the email in the sent box (it was encrypted with the sender’s public key).
Fake tokens was a bad way to put it - I was thinking about the alt tokens that admins have, but those aren’t linked to email.
Each email account has a set of keys, one public, one private. The public keys are published with the address listings. All the private keys are centrally (securely*) stored by the issuing authority. You might have a password on your Outlook pst folder, but that’s the extent of the protection. (It’s probably something easily cracked.)
Someone might have two current sets of keys - they might have one set for a personal account and one set for an organizational account. Or they might know someone who will set up a bogus account for them, but if they got a set of encryption keys, those keys are centrally held and if the court wants to know what’s in the emails, there is a hight probability they can find out.
My guess is they thought they were cute enough by having the second account and didn’t even bother with the keys, but that’s just my guess.