Two questions:

1. What is the purpose for the word "co-conspirator?" The word "conspirator" appears to be the correct term in usage. If the purpose is a function of attorney bafflegab - that is, never use one word when ten will do - I understand; co-conspirator has no purpose.

2. Why is the phrase "enter into" used when, in nearly all circumstances, the term "enter" furnishes accurate information? Another way of phrasing the question might be: Has anyone ever "entered out of?"

It's "exited out of " !!

The co-conspirator thing annoyes me greatly . It certainly is a non-word but sadly it's now in the dictionary .
Years ago the radio and TV anchormen could be looked to for proper pronounciation and usage but that's no longer true .They are certainly responsible in great part for the misuse on co-conspirator.

I agree that co-conspirator does not need to exist, but it's fairly easy to see why its use came about. In law a conspiracy is two or more people entering into an agreement for an illegal act or legal act for illegal objectives. There is no such thing as a single conspirator forming a conspiracy (or by definition it's not a conspiracy). But, like the term co-worker, it allows one to identify with which other conspirator he is aligned.