Does a prosecution have a duty to obtain a written statement from a witness?

clarifying, "We do not suggest . . . that a party has a duty to obtain a written statement from a witness, even if the witness is ready and willing to give such a statement"].) Neither the discovery statute nor the federal constitution compels the prosecution to obtain witness statements in order to disclose them to the defense. (See People v. Zambrano (2007) 41 Cal.4th 1082, 1163 [prosecution "need not extract all possible information from a private citizen who is a potential prosecution witness in order to disclose it to the defense"], disapproved on another ground by People v. Doolin (2009) 45 Cal.4th 390; cf. People v. Verdugo (2010) 50 Cal.4th 263, 287 ["Although defendant claims he was 'taken by surprise and . . . unable to effectively counter this new evidence [notes of detective's mid-trial examination of vehicle], the prosecution had no duty to obtain the evidence sooner than it did"], citing Littlefield, supra, at 135; Panah, supra, at 460 [relying on Littlefield to hold that prosecution committed no misconduct by failing to ask expert to prepare report sooner].)