What is the legal test for impeaching a testifying defendant based on moral turpitude?

Since the 1982 enactment of article 1, section 28 of the California Constitution (Proposition 8), a testifying defendant may be impeached with prior conduct that involves moral turpitude (i.e., a readiness to do evil). (People v. Castro (1985) 38 Cal.3d 301,

306, 313-316; People v. Wheeler (1992) 4 Cal.4th 284, 290-297, & fn. 7.)¹² Impeachment based on prior acts involving moral turpitude is premised on the recognition that "[m]isconduct involving moral turpitude may suggest a willingness to lie." (People v. Wheeler, supra, 4 Cal.4th at p. 295.) Prior to Proposition 8, only felony convictions were available for impeachment; after Proposition 8, any misconduct involving moral turpitude is available for impeachment, subject to the trial court's exercise of its discretion under Evidence Code section 352 to balance probative value against undue prejudice. (People v. Wheeler, supra, 4 Cal.4th at pp. 290-297, & fn. 7.)