Unlike in federal court, Missouri State Courts allow more flexibility regarding the use of prior convictions to impeach a witness. Section 491.050, RSMo provides, in part that:
“Any person who has been convicted of a crime is, notwithstanding, a competent witness; however, any prior criminal convictions may be proved to affect his credibility in a civil or criminal case and, further, any prior pleas of guilty, pleas of nolo contendere, and findings of guilty may be proved to affect his credibility in a criminal case.”
The Missouri Supreme Court has clarified that this statute confers “an absolute right, in both civil and criminal proceedings, to impeach the credibility of any witness…with his or her prior criminal convictions.” MAB v. Nicely, 909 S.W.2d 669, 671 (Mo. 1995). Importantly, a “conviction” occurs when a a “judgment of final condemnation has been pronounced against the accused.” Id. More recently, the Missouri Supreme Court has reiterated that prior convictions, even those not involving similar facts, may be used on cross-examination because when someone chooses to testify he or she “places his credibility in issue.” Mitchell v. Kardesch, 313 S.W.3d 667, 675 (Mo. 2010). Still, though, the trial court has discretion in deciding the nature and extent of a cross-examination. Id. at 670.