I know from personal experience that whenever anyone writes, he has an opportunity to think, consider, write, consider again, edit, and delete whatever comments he deems imprudent or rewrite to conceal that which he doesn’t want exposed. That which is written is always drafted with the audience in mind. How much do I want to tell them? How much do I want to conceal?
On the other hand, oral statements–especially when the speaker is under stress–are far less guarded, far less “edited,” and potentially much more revealing.
Thus, whenever you read a law book or even case law, you read a “sanitized” description of the law drafted by someone who is normally very astute as to what should and should not be revealed. But when you read trial transcripts, you can see the “real” law in its most unguarded, raw and sometimes brutal majesty. The difference between the case law written by judges and the transcripts of the trial are much like the differences between a biology book’s dry description of a feline’s digestive process and actually watching feeding time at the lion cage at the zoo.