Legal Question in Civil Litigation in California

Yes, so long as you serve the witness with an appropriate subpoena and pay the witness the appropriate mileage and witness fees. You would tell the judge at the time you call the witness that you are calling them under Evidence Code section 776, which allows you to examine the witnesses as if on cross-examination (which gives you the ability to ask leading questions, etc.). Remember, however, that you also have the right to cross-examine the witness after your opponent conducts their direct examination.

I agree with the other Mr. Hoffman. You should include that witness on your witness list if you plan to examine her directly, but you need not do so if you just want to cross-examine her.

You can probably also call her to testify without subpoenaing her or disclosing her on your list if she's in the courtroom at the time. But don't count on it. She may not show up for a variety of reasons, and even if she does you may not get a chance to call her. For example, if she shows up on a day when your opponent is presenting his case, the court may not let you interrupt in order to call her to the stand.