The court uses the language "in the first instance". So it sounds like you can use anything generated by the crime itself, but you can't dredge up other convers

The court uses the language "in the first instance". So it sounds like you can use anything generated by the crime itself, but you can't dredge up other conversations about the crime. Nixon ordering an illegal action is a crime, and Nixon destroying evidence was definitely a crime, so evidence of either would be game.