Does a prosecutor have a duty to learn of exculpatory or impeaching evidence that is in the hands of the government?

^16. Even though a prosecutor is actually unaware of exculpatory or impeaching evidence that is in the government's hands, the prosecutor has a duty to learn of any such evidence known to others acting on the government's behalf. This is because the prosecution is in a unique position to obtain information known to other agents of the government, and thereby to ensure the accuracy and fairness of trials by submitting all available evidence bearing on guilt or innocence to the adversary process. Carriger v. Stewart, 132 F.3d 463, 479-80 (9th Cir. 1997). It has been held that when the state chooses to use a career criminal as a witness, it is the state's obligation to turn over all pertinent information bearing on the witness's credibility, including criminal records and correctional files. Id. at 480.