Legal Question in Civil Litigation in California

Yes, if it's within the time limit for a demurrer or motion to strike the answer, which I believe is ten days, 15 if the answer was mailed to the plaintiff. After that either the plaintiff has to stipulate to it or you need to make a motion. Plaintiffs generally stipulate if its early in the case, since the court routinely grants the motions. If the case has been going along under one set of assumptions based on the answer, and you now want to change the game, you'll have a tougher time with the plaintiff, and a judge. You'll have to have a good reason why you didn't amend before, and most likely proof that the changes are meaningful and will be supported by evidence at trial.

Only if the answer has not yet been served on the other parties. If it has, the better approach is to get a stipulation form all parties and attach that and the proposed amended answer to your motion. If it is a relatively minor amendment, you might not need to make it or can get a stipulation from the other parties that it will be deemed amended [when you appear before the Judge at a conference, etc., you mlight be able to gtee him to issue without need of a motion that the answer is ameded].