Legal Question in Business Law in California

No one is ever ENTITLED to pay for testimony. If any person declines to testify voluntarily, they can be subpoenaed and if they do not appear they can be prosecuted for contempt of court. Once there, they must testify fully and truthfully or again face contempt of court charges or even perjury charges. All they are legally entitled to is the statutory witness fee and mileage, which amounts to something like $50/day. In addition, other than paid experts, it is a very bad tactical idea to pay a witness, since it blows their credibility. Add to all that, you are an employee, and therefore your employer is free to fire you if you do not fully cooperate with any work they have for you, including assisting with litigation. And then they can just subpoena you and the court will force you to testify. All that said, an appreciative employer may be quite willing to reward an employee who helps them with such an important matter. Just bear in mind in discussing that concept with your employer that you are ENTITLED to absolutely nothing.

If you are going to spend TIME for them, it would be reasonable to pay you for your time.

All the above is accurate, AND you should ponder whether the ex-employer could sue you or prevent you from disclosure of confidential info.

Any payment formula which, if discovered by the defendant, would undermine your apparent objectivity, should be avoided. For example, $50 an hour might be OK, but $100 an hour if we win is NOT ok. When you take the witness stand, you may be asked about compensation for your testimony.