Quote Originally Posted by Timon View Post
Thanks. It made me smile because I am a lawyer so I need to care. And I just want to understand the reason. I like the option saying that "plaintiff" without the determinder is just a replaced name of a man who is suing someone. But I do not believe that this is correct because in all such sentences the author speaks generally. And even in one sentence he uses both variants (with and without the determinder). I am completely confused
OK, in that case maybe it helps to see the words as variables or placeholders. You could supply A and B for plaintiff and defendant, and A and B would not take articles either.

Furthermore it is not necessary for the article to be used only if it's a reference to a specific plaintiff Bob or a specific defendant Mary. Even when speaking generally you could write something like this (example for grammatical purposes, not for meaning!): Every suit includes a plaintiff and a defendant ("a" because we are introducing the concepts). It is the responsibility (definite article because while there may be more responsibilities than this one, it is the only one which interest us here) of the plaintiff (definite article because in a given suit there is exactly one) to prove the guilt (definite article because a further definition follows) of the defendant (definite article for the same reason as with "plaintiff").

And in legalese the definite articles can be dropped from "plaintiff" and "defendant" because they are placeholders.