Legal Question in Civil Litigation in California

Enough to cover any potential defendants who you do not or may not know about... generally, in - say - a personal injury accident, 20 is a safe number.

Depends on the underlying case and how many unknown defendants you suspect may be involved. Out of hundreds of cases that I have been involved in, I required only needing one DOE defendant in my practice. That's because I waste so much time figuring out who is really responsible. 20 is the general number as Mr. Reed points out for auto cases, but if your case is auto, it depends on how big the car pile up was.