McClenahan v. Keyes

In McClenahan v. Keyes (1922) 188 Cal. 574, the court said: "The law fixes the fees of a witness and the only obligation incurred in the summoning of a witness is the obligation to pay the fees which the law fixes for the attendance of a witness. If there is any further or additional obligation it must arise from an express contract relating to the particular subject of the testimony and based upon the fact that the witness is required to use his expert knowledge in testifying."