Can a witness's prior inconsistent statements be used to test his credibility?

^17. Defendant's reliance on People v. Underwood (1964) 61 Cal.2d 113 is misplaced, as that case involved the prosecution's use of a witness's involuntary statements to the police for purposes of impeachment. (Id. at pp. 117-118.) In light of the use of involuntary statements, the Underwood court found it was error to give an unqualified instruction that a witness's prior inconsistent statements could be used for purposes of testing his credibility. (Id. at p. 125.) Nothing similar occurred below.