Can a witness be admitted as a witness in a civil case?

testimony can be admitted if the witness is unavailable and if the defendant was a party to the earlier action and had the right and opportunity to cross examine that witness. (Evid. Code, 1291; People v. Friend (2009) 47 Cal.4th 1, 67.) A person is unavailable as a witness if the party seeking to introduce their earlier testimony used reasonable diligence to secure their attendance but was unable to do so through the court's process. (Evid. Code, 240, subd. (a)(5).)

Reasonable diligence in this context is the same as due diligence. (People v. Fuiava (2012) 53 Cal.4th 622, 675.) Although there is no rigid definition of due diligence, it suggests perseverance and untiring and earnest efforts of a substantial character. (Ibid.) Relevant considerations include whether efforts to locate the witness were timely, the importance of the witness's testimony, and whether leads to his whereabouts were competently explored. Because the facts surrounding the prosecutor's efforts to locate Herrera and Tolai are undisputed, our review is de novo and we independently determine whether the prosecutor exercised the proper diligence to secure the witnesses' attendance at trial. (Ibid.)